Italy: SIP providers and connecting a number to the PBX

This page continues the general guide on connecting a provider's number to the PBX: that one covers everything that is the same for any carrier — the two trunk modes, what to ask the provider, what to type into the form, network requirements and the connection test. Here is the Italian specifics: who sells a number with a SIP trunk in the country, what such a carrier hands out and what of it goes into Telephony → "Trunks and connections" → "Add provider".

The data was collected on 9 September 2026 from carrier documentation and regulator (AGCOM) materials; the links are in the "Sources" section.

In brief#

• You can buy a number with a SIP trunk in Italy, and the venue needs no permits for it. There is no VoIP licence in the country: the carrier operates under a general authorisation plus a numbering assignment from AGCOM, and you are simply its subscriber.
• The market splits in two, and this is the country's main fork. "Internet carriers" (MessageNet, OlimonTel, VoipVoice, Vianova, TWT, infoSet…) sell a trunk you can point anywhere. With access carriers — TIM, Vodafone, WINDTRE, Fastweb — the SIP trunk is tied to their own internet line at the venue: registration is accepted only from that line. Such a trunk never reaches a PBX in the cloud.
• If the carrier is not chosen yet, take MessageNet: the account is opened online, the host, ports and codecs are published, and the guide is written specifically for Asterisk. The second most transparent is OlimonTel. Both work in registration (REGISTER) mode.
• The main local pitfall — the incoming call carries a login, not a number. Both MessageNet and OlimonTel do this: the call reaches the PBX and is handled, but you cannot pick a line by it until the carrier enables the "selezione passante" service (delivery of the dialled number) on the account.
• The second pitfall is the leading zero. In Italy 0 is part of the number, not a "dial out" prefix: +39 02 … is written with the zero. The last seven digits, by which the PBX recognises a line, cut off the district code of a 10-digit Italian number entirely — two Milan numbers may share the same tail.
• Paperwork. The contract is signed with an Italian entity or an individual holding a codice fiscale / partita IVA; MessageNet accepts a European ID card, a driving licence or a passport plus a selfie with the document. A geographic number gets a "domicilio" — the address of the district it is tied to.

Numbers in Italy#

• Country code — +39. The national number is 3 to 12 digits depending on the type of service.
• The leading 0 is part of the number, not a dial-out prefix. The first digit defines the kind of number: 0 — geographic, 3 — mobile, 5 — nomadic (VoIP), 8 — toll-free and premium. In international format the zero is not dropped: the Milan number 02 1234 5678 is +39 02 1234 5678, not +39 2 … (unlike France, Germany or Poland).
• Geographic: district code 02 (Milan), 06 (Rome), 011 (Turin), 055 (Florence) and so on; the whole number is at most 10 digits, at least 6 (up to 11 if the digit right after the district code is 1).
• Mobile: ranges 31 and 32–39, 10 digits (at least 9), with no leading zero.
• Nomadic VoIP numbers — the 55 decade, exactly 10 digits. They are not tied to a district, but they do not look "local" to a guest either.
• Toll-free 800… (numero verde) — 9 digits; premium — 89….
• Dialling. Inside the country the number is dialled in full, with the leading zero for geographic numbers and without it for mobile ones; abroad — 00 plus the country code, or +. Emergency services: 112 (single number), 113 police, 114 child helpline, 115 fire brigade, 118 ambulance, 1530 sea rescue.

On the "Lines" tab the number can be entered in any form: the PBX compares the last seven digits. ⚠️ In Italy seven digits are the number without the district code, so 02 1234 5678 and 02 9234 5678 give different tails, while 02 1234 5678 and 06 1234 5678 give the same one. With several numbers on one trunk, check the tails by hand — "Add a number and routing".

⚠️ Emergency numbers are shorter than four digits. A general outbound rule of the "everything else goes through this trunk" kind does not pick them up: create separate rules with an explicit pattern for 112, 113, 115 and 118 on the "Outbound" tab. This is a regulator's requirement, not a convenience.

Who sells a number with a SIP trunk#

The first three rows are carriers whose parameters are in open documentation: their cards are below. The next six have their own contract-only section: they issue the server address and password after a contract is signed. The four access carriers are covered separately — with them the scheme does not work at all.

MessageNet#

A Milan VoIP carrier with full self-service: the account is opened online and the number is issued after an ID check. The only one in the country that keeps a public and up-to-date guide written specifically for Asterisk — with a ready configuration, caller ID handling and fax. For a venue this is the fastest route: from sign-up to the first call it usually takes hours, not weeks.

What to enter in the admin panel

What to set up at the provider: sign up → upload a document and a selfie → buy or port a landline number, stating the "domicilio" → point the number to the URI in the portal → if there is more than one number, ask to enable "selezione passante" and number presentation.

Pitfalls ⚠️ Two different passwords — one for the website and one for the URI; the trunk form needs the second one, and this is the most common cause of "the credentials are right but there is no registration". The incoming call carries the login, not the number until "selezione passante" is enabled — the call is handled, but you cannot pick a line by it. The carrier has no encryption at all: neither TLS for signalling nor SRTP for media — that suits our PBX, but a venue that requires encryption needs another carrier. The carrier's own recommendations put G.729 first, and the PBX does not speak it: G.711 a-law is always on the list, but it is worth stating this when ordering. The platform does not support transferring a call outwards by SIP means (REFER and 302) and caps traffic at 10 calls per second; the registration interval is no shorter than 300 seconds. Source: Asterisk (PJSIP), Caratteristiche piattaforma, Codec audio — 09.09.2026.

OlimonTel#

Another Milan carrier with retail VoIP and its own cloud PBX. It publishes a full set of technical parameters — ports, the media port range, its own networks and a sample Asterisk configuration with the registration string. The second most transparent documentation in the country.

What to enter in the admin panel

What to set up at the provider: order or port a number → get the Welcome Letter with the login, password and domain → with several numbers, order "selezione passante" (GNR) → confirm that registration is allowed from your PBX's public address.

Pitfalls ⚠️ The "SIP host" field needs a name, not an IP address: the carrier checks the domain during authorisation, and a bare address will not register. The login is sent together with the carrier's domain — the PBX substitutes it itself from the "SIP host" field, so there is no need to append @sip2.olimontel.it in the "Login" field. The incoming call carries the login, not the number, just as with MessageNet. The native codecs are G.729A and G.711 a-law, everything else is transcoded; ⚠️ transcoding breaks fax, so a venue that uses fax should agree the codecs in advance. Without a valid registration the carrier blocks outgoing calls (incoming ones still arrive). The typical 403 Unknown User rejection means the call went out from a different address or port than the registration did. Source: Configurazione Asterisk PBX, Informazioni Tecniche VoIP — 09.09.2026.

VoipVoice#

A Florence carrier that sells only through integrator partners: there are no public prices and no online ordering, but the technical guides are open and the line can be pointed to your own PBX. A sensible choice if the venue already has an IT person or a system integrator.

What to enter in the admin panel

What to set up at the provider: find a reseller partner → order the number and the number of channels (4–30 on the pay-per-minute plan, 1–15 on the flat one) → get the domain, login and password → check whether registration is allowed from an arbitrary address, since the PBX sits in the cloud.

Pitfalls ⚠️ Every customer has its own host — the carrier has no shared constant that could be filled in beforehand: take the domain from the activation letter, not from someone else's guide. The public guide is dated 2019, so check the parameters against what arrived at activation. The carrier does not publish its codecs: ask the partner to confirm G.711 a-law in writing — that is the one the PBX speaks for sure. The carrier's network requirement (static port mapping, SIP ALG disabled) applies to an on-premises PBX; a cloud PBX already has a static address. Source: Guida alla configurazione linea VoipVoice su PBX Tvox, routing and NAT requirements — 09.09.2026.

Contract-only carriers#

These carriers do have a SIP trunk for a third-party PBX and sell it as a standard product, but the server address, login and password are issued only after a contract — so there can be no "what to enter" table here. Ask the account manager for the parameters using the list from "What to ask the provider" and type them into the same form as for the others. One thing deserves a separate mention: the PBX sits in the cloud, not on your premises — get that confirmed in writing before paying.

• Vianova (Welcome Italia) — the only carrier that promises both IP authorisation and registration in its public product description, and explicitly mentions working "over another carrier's connectivity". The trunk is delivered through their own SBC and is declared compatible with IP PBXs "in the cloud or on site". The published package: 1 channel, a landline number, an 800 number and fax — 15 € activation, 25 € per month; "selezione passante" for 10, 100 or 1000 numbers is a separate item. The host, port and codecs are issued at activation; the description mentions SIP/TLS and SRTP — confirm that the trunk can also run over plain UDP or TCP, which the PBX understands. For the IP mode, give the carrier the "Static IP" from the "Server" tab.
• TWT S.p.A. — a Milan carrier with its own network and interconnects with 70+ operators. The mode is registration; the login is the trunk's main number in national format, with the leading zero (0597353000). Outbound caller ID — only numbers from your account. Important for us: the carrier has a standard procedure for a PBX in someone else's cloud — you tell them the station's address (FQDN), after which registration from outside is allowed.
• infoSet — a carrier and system integrator. It states the same thing more plainly than anyone in the country: send your PBX address to support, they validate it and allow the trunk to register from any IP. The login, as with TWT, is the trunk number with a leading zero. ⚠️ Until the address is validated, registration is rejected and looks like a wrong password.
• Trenove — a carrier from Vicenza, certified as a SIP provider by both 3CX and Yeastar, which means a trunk to a third-party PBX is standard for it. It publishes no parameters of its own and sells by project: for a single venue this carrier is rather oversized.
• Ehiweb (Ehinet) — a retail carrier with online number activation, including the "Numero Pro" business plan. SIP parameters are issued in the customer portal after activation. Before connecting a venue, check the number of simultaneous channels and make sure the plan allows your own PBX and not only their virtual one.
• Retelit (ex Irideos, ex Clouditalia, ex Eutelia) — a large corporate carrier into which three historical brands merged: old instructions for Eutelia and Clouditalia found online lead nowhere. Connection is project-based and includes agreeing your PBX address; for a single venue it makes sense only if Retelit already serves it.

TIM, Vodafone, WINDTRE and Fastweb — why they will not work#

This is the country's main filter, and it is better to hit it before paying. All four carriers hand the subscriber VoIP parameters — under the Italian rule obliging a carrier to make connecting your own equipment possible — but they accept the trunk only from their own access line:

• TIM ("TIM TRUNKING Comunica"): the documentation says outright that the trunk can be registered exclusively from the data line the telephone service is tied to. On top of that, their proxy address resolves only through the carrier's DNS, so from the internet it is simply invisible.
• WINDTRE Business: the same model — registration only from the tied line, the address resolved by their DNS; in the corporate variant the trunk is delivered through carrier equipment with a private subnet at the handover, which has no route from the internet at all.
• Vodafone Italia: the platform domain (ims.vodafone.it) and the proxy do not resolve outside the Vodafone network. Plus a separate "VoIP line password" that differs from the portal password and has to be requested from the carrier.
• Fastweb: the trunk is set up towards an SBC standing in the venue's local network, without authorisation, and the documented configurations agree on the G.729 codec, which the PBX does not understand. Two stoppers at once.

Something common to all four: the carrier's own modem keeps registering the same account in parallel with the PBX and "eats" incoming calls — it is either replaced or switched to internet-only mode.

What to do if the number is already with one of them. There are two options: take a second number from an internet carrier from the cards above and move guest calls to it — or port the existing number using the Italian MNP procedure. A third option is to keep a PBX on the venue's premises with that carrier, but that is no longer our scheme.

International providers with Italian numbers#

Italian numbers are sold by Telnyx, Twilio, DIDWW, Plivo, Bandwidth, Sinch, Vonage and Sonetel. For a foreign company this is often the only way: a local carrier signs the contract with an Italian entity and requires a codice fiscale or partita IVA, plus an Italian "domicilio" for a geographic number.

• They will still ask for documents. Italy is on the lists of countries with regulatory requirements for numbers: for a landline +39 they will ask for proof of address and business registration. The exact set depends on the number type and is shown in the provider's portal when ordering.
• The modes differ. Telnyx and DIDWW offer both registration and a static IP endpoint; Twilio Elastic SIP Trunking works by IP only — you will need the PBX's static address from the "Server" tab. Telnyx and Twilio cards already exist in the catalogue when adding a provider: the server address and mode are filled in automatically.
• ⚠️ Keep the Italian anti-spoofing filter in mind. Since 19 August 2025 (for fixed numbers) and 19 November 2025 (for mobile ones), carriers block international calls entering Italy that present an Italian number which could not be verified. If your outbound traffic leaves an international provider from a site outside Italy and presents an Italian number, it may hit that filter. Before going live, ask the provider in writing whether its Italian outbound traffic goes through the national interconnect.

Porting a number#

• Porting works through the "codice di migrazione" — the number's secret code, which the previous carrier is obliged to give the subscriber. The request is filed with the new carrier, and the code goes to it as well. With retail carriers the code sits right in the number's card in the customer portal.
• Timing — on average 3 to 10 working days depending on how complex the request is; after the contract is terminated the right to port is kept for 60 days.
• Porting an ISDN "multi-number" (several numbers on one legacy line) is a separate procedure with caveats: some services are lost in the process, and carriers document the details separately.
• The number is registered to whoever passed the document check. With retail carriers the contract is signed online in a specific person's name: if the number is for the venue, register it to the partita IVA straight away, otherwise it leaves with the person when the business changes hands.
• The geographic number's "domicilio". If the venue moves to another district, the number formally stays yours, but the address in the contract must be updated: emergency call routing is built on it.

Rules and paperwork#

If it does not work#

1. Calls arrive, but always on the same line. With MessageNet and OlimonTel the incoming call carries the SIP login, not the dialled number. Until the carrier enables "selezione passante", two numbers cannot be told apart in routing — order the service or keep a single number on the trunk.
2. No registration, although the login and password are "correct". Check that it is the right password: with MessageNet the URI password differs from the customer portal password, with Vodafone the "VoIP line password" differs from the portal one. And that it is the right login format: with TWT and infoSet the login is the number with the leading zero, with access carriers it comes with +39 or 39. A format mistake looks exactly like a wrong password.
3. OlimonTel answers 403 Unknown User. The "SIP host" field holds an IP address instead of a name, or the call leaves from a different address or port than the registration did. Enter the domain name from the Welcome Letter; if a SIP ALG interferes between you and the carrier, try port 5062.
4. An access carrier's trunk does not come up at all. TIM, Vodafone, WINDTRE and Fastweb accept registration only from their own line, and their server addresses do not resolve from the internet — why that is and what to do.
5. The call connects but there is silence. Only G.729 is agreed on the account: it comes first in the MessageNet and OlimonTel recommendations and is the only one in Fastweb configurations. Ask the carrier to enable G.711 a-law.
6. Outbound calls are rejected or go out with a different number. The carrier only passes numbers tied to your trunk. With MessageNet, choosing among several numbers is a separate feature enabled on the account; while it is off, the carrier substitutes the trunk number.
7. Two numbers land on the same line. The last seven digits of an Italian number contain no district code — numbers from different cities may share a tail. Separate such lines by hand.

Causes that do not depend on the country are in "If calls do not get through"; the SIP trace in the trunk menu is described there too. Checking the address and port — "Check the connection", transport and codec requirements — "Network and compatibility".

Frequently asked questions#

Which carrier should I choose if nothing is connected yet?#

MessageNet: the account is opened online, the number is issued after a document check, and the host, ports and codecs are published — there is nothing to hunt for when filling in the admin panel. The second option is OlimonTel, which also publishes everything. If the venue needs IP authorisation and a contract with a business carrier, look at Vianova, but there the parameters are issued only after activation.

My number is with TIM (Vodafone, WINDTRE, Fastweb). Can I connect it to the PBX?#

Not directly: their trunk registers only from the internet line the telephone service is tied to, and the PBX sits in the cloud. There are two ways out: take a second number from an internet carrier and move guest calls to it, or port the existing number through the MNP procedure with the "codice di migrazione".

Do I need an Italian company to get a number?#

For a local carrier — yes, the contract is signed with an Italian entity or an individual with a codice fiscale or partita IVA, and a geographic number requires a stated "domicilio". A passport is on the list of accepted documents, so a foreigner can pass the check in principle, but the tax number and the Italian address of the number are still needed. For a foreign company without Italian registration it is easier to take a +39 number from an international provider.

Can I present a different number on outbound calls?#

Only numbers tied to your trunk. The carrier checks this on its side, and since 2025 there is also a national filter dropping international calls with an unverified Italian number. Fill the "Show as" field with your own numbers only.

Why do calls arrive but the wrong line is selected?#

Because the carrier sends its login in the call instead of the dialled number — that is how the basic MessageNet and OlimonTel setups work. Order "selezione passante" from the carrier: after that the dialled number appears in the call and the lines start to differ.

How many channels does a venue need?#

A channel is one simultaneous conversation. A restaurant usually needs 2–4: one is taken by a guest, the second by a courier or a supplier. Vianova's base package includes one channel and more are added as needed; with VoipVoice the number of channels depends on the plan (4–30 on the per-minute one, 1–15 on the unlimited one).

Sources#

All links checked on 09.09.2026.

Carriers

• MessageNet — Asterisk (PJSIP), full configuration example: https://helpcenter.messagenet.com/hc/it/articles/8008441680925-Asterisk-PJSIP
• MessageNet — Caratteristiche piattaforma (ports, networks, limits): https://helpcenter.messagenet.com/hc/it/articles/8867808481821-Caratteristiche-piattaforma-MessageNet
• MessageNet — Codec audio supportati: https://helpcenter.messagenet.com/hc/it/articles/229467388-Codec-audio-supportati-dal-VoIP-di-MessageNet
• MessageNet — Informazioni per la configurazione VoIP: https://helpcenter.messagenet.com/hc/it/articles/229469848-Informazioni-per-la-configurazione-VoIP-MessageNet
• MessageNet — I numeri VoIP (URI, codice di migrazione, domicilio): https://helpcenter.messagenet.com/hc/it/articles/360006735018-I-numeri-VoIP
• MessageNet — Modifiche nella piattaforma VoIP: https://helpcenter.messagenet.com/hc/it/articles/24359939075997-Modifiche-nella-piattaforma-VoIP
• MessageNet — which documents are accepted at the identity check: https://helpcenter.messagenet.com/hc/it/articles/4414694237329-Perch%C3%A9-il-mio-documento-%C3%A8-stato-rifiutato
• OlimonTel — Configurazione Asterisk PBX VoIP: https://olimontel.it/guide-configurazioni/guida-configurazione-asterisk-pbx-voip/
• OlimonTel — Informazioni Tecniche servizio Numero VoIP: https://olimontel.it/guide-configurazioni/informazioni-tecniche-voip/
• VoipVoice — Guida alla configurazione linea VoipVoice su PBX Tvox (PDF): https://www.voipvoice.it/wp-content/uploads/2019/05/Guida-Tvox.pdf
• VoipVoice — routing and NAT requirements: https://www.voipvoice.it/routing-nat-voip/
• Vianova — SIP Trunk, description and pricing: https://www.vianova.it/fisso/sip-trunk/
• TWT — Servizi Voce: https://www.twt.it/servizi/voce/
• infoSet — VoIP telephony / SIP trunk provider: https://www.infoset.it/en/voip-telephony-trunk-sip-provider/
• Trenove — telecom services for business: https://www.trenove.net/
• Ehiweb — Numero Pro: https://www.ehiweb.it/business/voip/numero-pro/
• Retelit — Voce / Cloud PBX: https://www.retelit.it/it/voce/cloud-pbx
• TIM Business — TIM TRUNKING Comunica: https://timbusiness.tim.it/fisso/centralini/voip
• WINDTRE Business — Centralini Virtuali: https://www.windtrebusiness.it/partita-iva-aziende/fisso-e-internet/centralino-virtuale
• Allnet.Italia — a walkthrough of the TIM trunk on a third-party PBX: https://docs.allnet-italia.it/kb/trunk-sip-tim-su-ucm/
• Allnet.Italia — a walkthrough of the WINDTRE trunk on a third-party PBX: https://docs.allnet-italia.it/kb/trunk-sip-windtre-su-ucm/
• 3CX — TWT SIP Trunk Configuration Guide (Italy): https://www.3cx.com/community/threads/twt-sip-trunk-configuration-guide-italy.79820/
• 3CX — infoSet SIP Trunk Configuration Guide (Italy): https://www.3cx.com/community/threads/infoset-sip-trunk-configuration-guide-italy.79817/
• 3CX Italia — trunk configuration with a Fastweb SBC: https://www.3cx.it/community/threads/configurazione-trunk-con-sbc-fastweb.113692/

Regulator and numbering

• AGCOM — the numbering plan and emergency numbers: https://www.agcom.it/competenze/comunicazioni-elettroniche/reti/numerazione/piano-di-numerazione
• ITU-T — national numbering plan for country code +39 (PDF): https://www.itu.int/dms_pub/itu-t/oth/02/02/t020200006b0001pdfe.pdf
• AGCOM — annex to delibera 11/06/CIR on VoIP numbering and the district tie (PDF): https://www.agcom.it/sites/default/files/migration/attachment/Allegato%2007-03-2006.pdf
• AGCOM — press release on the anti-spoofing filter (delibere 106/25/CONS and 271/25/CONS): https://www.agcom.it/comunicazione/comunicati-stampa/comunicato-stampa-62

Related pages#

• Connecting a provider's number to the PBX — the common steps, trunk modes, network, connection test.
• Setting up SIP phones — how to connect desk phones and DECT to extensions.