Serbia: 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 are the Serbian specifics: who sells a number with a SIP trunk in the country and what of the issued data goes into Telephony → "Trunks and connections" → "Add provider".

The data was collected on 9 September 2026 from carrier websites, materials of the regulator RATEL and the acts in force; the links are in the "Sources" section.

In brief#

• You can buy a number with a SIP trunk in Serbia, and the venue needs no permits for it. Numbering is assigned by the regulator RATEL, but not to you — to the carrier: you are simply its subscriber buying a number and a channel.
• The country's main fork is where the trunk physically arrives. Both large carriers, Telekom Srbija (mts) and SBB, do have a "SIP trunk" product, but the channel arrives over their own network with private addressing — a cloud PBX cannot reach such a trunk under any settings. Why that is and what to do.
• If the carrier is not chosen yet, the local candidate number one is SoftNET: a regional carrier with its own SBC, IP authorisation mode and numbers in Belgrade, Novi Sad and Niš. The fast route without a Serbian contract is Zadarma (numbers 011, 018, 021, 024, 019 and 0800, registration mode).
• The main local pitfall is the geographic tie of the number. The numbering plan allows a geographic number to be used on "smart" devices through an app only if you have a matching connection at a fixed location in that geographic zone; sellers phrase this as "confirm your physical presence in the city". A "Belgrade number for a venue with no office in Belgrade" is not always a lawful configuration.
• The second pitfall is matching number tails. The PBX recognises a line by the last seven digits, and in Belgrade and Novi Sad the subscriber part is exactly seven digits long: 011 3033000 and 021 3033000 produce the same tail.
• Paperwork. A local carrier signs the contract with a legal entity (APR extract, PIB and company registration number) or with an individual holding an ID card; international providers ask for a copy of the company registration certificate and proof of the current address.

Numbers in Serbia#

• The country code is +381, the national prefix is 0, the international prefix is 00.
• Geographic numbers: the zone code (NDC) is two digits, exceptionally three, and starts with 1, 2 or 3; the subscriber part is 6 or 7 digits and does not start with 0, 1 or 9. Main zones: 11 Belgrade, 21 Novi Sad, 18 Niš, 24 Subotica, 34 Kragujevac, 19 Zaječar, 31 Užice, 32 Čačak, 36 Kraljevo.
• Mobile: an NDC of 2–3 digits starting with 6 or 5, subscriber part of 6–7 digits.
• Non-geographic: 70x — universal access number, 76 — nomadic voice service (the Serbian equivalent of a European "VoIP range"), 800 — toll-free, 900, 901, 904–906, 909 — premium rate.
• Dialling. Inside one geographic zone — the subscriber number alone; in every other case 0 + zone code + number (011 XXXXXXX); from abroad — +381 11 XXXXXXX; outbound — 00 and the country code.
• Emergency services: 112 (single number), 192 police, 193 fire brigade, 194 ambulance, 1985 civil alert.

On the "Lines" tab the number may be entered in any form — with +381, with a leading zero or with no code at all: the PBX compares the last seven digits. ⚠️ In Serbia seven digits in large cities are exactly the subscriber number without the zone code, so numbers from different cities may share a tail. With several numbers on one trunk, compare the tails by hand — "Add the number and routing".

⚠️ Emergency numbers are shorter than four digits. The general outbound rule "everything else goes through this trunk" does not catch them: create separate rules with an explicit pattern for 112, 192, 193 and 194 on the "Outbound" tab.

Who sells a number with a SIP trunk#

The first three rows are the ones whose parameters are known and which have a card below. SAT-TRAKT and the carriers without a public product are covered in the "contract-only" section, and the two largest carriers separately: with them the scheme does not work at all.

SoftNET#

A private regional carrier with its own IP network and offices in seven countries (Slovenia, Croatia, Serbia, Bosnia and Herzegovina, North Macedonia, Bulgaria, Romania); the Serbian office is at Vladimira Popovića 40, Novi Beograd, +381 11 42 20 200. Its telephony is split into three products: SIP trunking, IP Centrex and On site IP-PBX; you need the first one. This is the only Serbian carrier whose mode is publicly described as "the trunk is handed over with IP authorisation to your SBC": the analysis by the 3CX partner Creomate lists "IP-based trunks", an "Allowed IP address list", DTMF RFC 2833 and E.164 number formatting, with numbers in Belgrade, Novi Sad, Niš and 800.

What to enter in the admin panel

What to set up with the provider: order SIP trunking for a legal entity → hand the carrier the "Static IP" from the "Server" tab for the "Allowed IP address list" → agree on the number of simultaneous channels → ask for the purchased DIDs to be delivered to the trunk in E.164 format → confirm the codecs: the PBX speaks G.711 a-law, G.711 u-law and G.722, and does not understand G.729.

Pitfalls ⚠️ SoftNET itself does not publish trunk parameters: take the host, port, transport and codecs from the contract and confirm them in writing before paying — above all the fact that the trunk is delivered to an external static address over the public internet. The carrier also sells its own PBX (IP Centrex, On site IP-PBX), so the sales manager will offer that by default — insist on the trunk. The carrier is regional: verify that the issued DIDs really are Serbian and not from a neighbouring country. Source: SoftNET — Telefonija, Creomate — DID VoIP-trunks Srbija, Creomate — 3CX Generic SIP trunk to SoftNET SBC — 09.09.2026.

Creomate#

An integrator and reseller from Novi Sad (3CX Advanced Partner, +381 21 3220 030): not a carrier but an intermediary that sells Serbian DIDs and connects them to the customer's PBX. It keeps the only public page in the country where trunk modes are listed per donor carrier: SoftNET and Telekom Srbija — "IP-based trunks" with an allowed address list, DTMF RFC 2833 and numbers in E.164; Zadarma — "registration-based". A sensible route if the venue needs a number in a specific city and has no time to negotiate with a carrier itself.

What to enter in the admin panel

What to set up with the provider: order a DID in the city you need → hand over the "Static IP" from the "Server" tab for the allowed list → ask for the number in the Request-URI in E.164 format → agree on the number of simultaneous channels → ask up front who the donor carrier is: both the mode and the server address depend on it.

Pitfalls ⚠️ The intermediary adds its own margin and its own SLA, while the trunk parameters still come from the donor carrier — troubleshooting travels along that chain. The Creomate claim that the Telekom Srbija trunk is handed over "by IP" contradicts the carrier's own subscriber scheme (registration and a private proxy, see below): most likely it refers to a wholesale connection available to a reseller rather than to an ordinary venue — clarify this before ordering. The same page states the market rule: when buying a local number the buyer must confirm physical presence in the city. Source: Creomate — DID VoIP-trunks Srbija, Creomate — 3CX Generic SIP trunk to SoftNET SBC — 09.09.2026.

Orion telekom#

A Serbian alternative carrier (internet, IPTV, fixed telephony, business ICT). Its separate Orion VoIP service is about cheap international calls from an IP phone, an ATA adapter or a gateway: "compatible with many IP phones supporting the SIP standard". Its value for us is that this is the only Serbian carrier with publicly published SIP parameters — they live in its softphone setup guide.

What to enter in the admin panel

What to set up with the provider: register at moj.oriontelekom.rs → activate the Orion VoIP service → top up the credit → ask support for the current host, port and codec list.

Pitfalls ⚠️ This service provides no inbound number — it is about outbound international calls; Orion sells landline numbers separately, inside fixed telephony packages, and a trunk to them is not publicly described. In its own FAQ the carrier writes that calls to Serbian fixed and mobile numbers through this service technically travel "via abroad" and are not recommended — it is not suitable as a venue's main channel. The service pages are dated 2010: verify the parameters with support before connecting. The carrier publishes neither codecs nor the DTMF mode. Source: Orion VoIP — SIP parameters, Orion VoIP preko Interneta, FAQ — 09.09.2026.

Contract-only carriers#

These carriers cannot have a "what to enter" table: they publish no parameters at all and issue them after the contract is signed. Ask for them using the list in "What to ask the provider" and type them into the same form. Raise the key point separately and in writing: the PBX sits in the cloud, not on the venue's premises — in Serbia this is the decisive question.

• SAT-TRAKT — a cable operator in northern Vojvodina (Bačka Topola, zone 024), the only one in the country that spells out exactly the scenario we need: "the user already has a modern PBX supporting SIP trunk interconnect — and this is also the recommended way of implementation"; for older PBXs it offers POTS and ISDN. Caller ID, number withholding, call forwarding, call waiting, voicemail and destination barring are free; porting a number in from other fixed networks is free; there is a portal with call statistics. Contact — 024 4 155 155. ⚠️ The service is tied to the carrier's network area: it is of no use to a venue in Belgrade.
• A1 Srbija — the Serbian storefront has no "SIP trunk" or "IP Centrex" product: only mobile plans, business internet, VPN, IoT, cloud and security. Sister companies of the group do have one (A1 Hrvatska "Biz IP Trunking", A1 Slovenija "A1 PBS"), so asking the business department (060 1230) whether a trunk is sold on request does make sense. A1 offers a Serbian landline number to private subscribers through porting.
• Yettel Srbija — the former Telenor: mobile service, fibre internet, TV, business plans. There is no public SIP trunk; ask the business department (063 9000). For us it is a source of mobile numbers and internet, not of a channel for the PBX.
• BeotelNet-ISP — a Belgrade provider with digital fixed telephony aimed primarily at its own internet subscribers. There is no "SIP trunk for your own PBX" product on the site: ask whether they issue a SIP account instead of an ATA adapter.

Telekom Srbija and SBB — why the trunk never reaches a cloud PBX#

This is the country's main filter, and it is better to hit it before paying. Both carriers name the product correctly and do sell it, but the channel arrives over their own network:

• Telekom Srbija (mts), "Business Trunking". The description is exactly what is needed: "connecting your SIP-capable PBX to the platform", a choice of the number of lines, an SLA, connecting several PBXs at different locations, 30 days of free trial; ordering goes through the business department (0800 100 100) and the price is not published (for reference: an ordinary fixed business line costs RSD 659/month including VAT). But the settings the carrier hands out to subscribers consist of the addresses 10.0.0.2 (outbound proxy ims.telekomsrbija.com), 10.10.8.4 (the second node) and 10.10.3.146 (NTP). These are private addresses that are not routed on the internet: the trunk lives on a separate carrier channel, and a PBX in the cloud will never reach it. Integrators who have connected such a trunk separately describe two network interfaces, static routes and a manual hostname entry in the hosts file — that is the "PBX on the venue's premises" scheme.
• SBB (Serbia Broadband). The product page consists of a single sentence — "have your own IP PBX? connect it"; no parameters, no tariffs, everything through the sales department (19966). According to integrators' accounts, SBB — unlike Telekom Srbija — does issue a written guide, the mode is registration, and the credentials go to the legal entity that bought the SIP Trunk (an individual with a phone on an ATA adapter is given no login and password). The same accounts mention the private address 10.248.0.17, and public hostnames such as sip.sbb.rs or voip.sbb.rs do not exist in DNS (checked 09.09.2026) — so this trunk, too, lives inside the carrier's access addressing.

What to ask if you still want a trunk from them. One question by e-mail: "do you deliver the SIP trunk to an external static IP address over the public internet?" A "no" closes the subject; a "yes" — ask for a settings sheet with a public server address before signing the contract.

What to do if the number is already with them. Two options: take a second number from SoftNET, through Creomate or from an international provider and move guest calls onto it — or port the existing number; in Serbia the procedure takes no more than one working day and is free for the subscriber.

International providers with Serbian numbers#

For a foreign company without a Serbian legal entity this is usually the only route: a local carrier signs the contract with a Serbian entity. The trunk parameters of these providers are the same in every country — their cards are already in the catalogue when adding a provider, so the server address and mode are filled in for you.

• Zadarma — the widest set of Serbian numbers: 011 Belgrade, 018 Niš, 021 Novi Sad, 024 Subotica, 019 Zaječar and 0800. Setup costs $8, the monthly fee is $12 (a toll-free number, $28 and $33.6). Every number comes with two lines (two simultaneous calls); extra ones are charged separately. Paperwork: a copy of the company registration certificate, the current address (city, street, building, postcode) and the intended use of the number. The mode is registration.
• DIDWW — in Serbia it sells toll-free +381 800 numbers only: inbound calls and A-Z SIP trunking are listed, but local SIP trunking, emergency calling, number portability, SMS and fax are not. A 011 landline cannot be bought there.
• CommPeak, PBX.IM and Sonetel keep country pages for Serbia; which numbers exactly the offer covers — geographic, national or outbound termination only — should be confirmed in the portal when ordering.
• Telnyx, Twilio, Plivo, Bandwidth and Vonage do not publicly advertise Serbian numbers — check by searching in the provider's portal.
• ⚠️ The physical-presence requirement does not disappear. International providers read it as "an address in the country and the city in the application form", but the number is then issued against an address the venue may not have. Give the real address of your location: if it is checked, you are the one who will be asked.

Porting a number#

• Porting is the subscriber's right. The application is filed with the receiving carrier and simultaneously counts as termination of the contract with the old one; the disconnection and reconnection procedure may not last longer than one working day; the subscriber pays nothing for the port. The database of ported numbers is kept by RATEL.
• ⚠️ A geographic number can only be ported within its own location — the one its zone code belongs to. You cannot "take 011 along" to another city: when the venue moves, the number changes, unless the carrier keeps it within its own service (Telekom Srbija promises number retention when changing location inside its network).
• With alternative carriers, porting in from other fixed networks is free — SAT-TRAKT, for instance, states this explicitly.
• The number belongs to whoever passed the identity check. Porting identifies an individual (name, personal number, address), a foreigner (passport and issuing country) or a legal entity (company details). A number registered to an employee leaves with them — register it to the company.

Rules and paperwork#

If it does not work#

1. A large carrier's trunk does not come up at all. With Telekom Srbija and SBB the server address is private (10.0.0.2, 10.248.0.17) and does not exist on the internet. No setting on our side fixes that — why that is and what to do.
2. No registration although the login and password are correct. Check the login format: with Telekom Srbija it is the number in E.164 without the + (38111xxxxxx), while the authorisation name looks like <number>@<carrier domain>. A wrong format looks exactly like a wrong password.
3. Calls do not arrive in IP authorisation mode. The PBX address did not make it into the carrier's "Allowed IP address list". Copy the "Static IP" from the "Server" tab and hand it to the carrier; "Test the connection" helps verify the path to the server.
4. The call connects but there is silence. Serbian carriers do not publish codecs, and the Telekom Srbija network uses G.711 and G.729 as standard, with G.722 as the wideband option. Ask the carrier to agree on G.711 a-law: our PBX does not understand G.729.
5. Two numbers land on the same line. The last seven digits of a Belgrade or Novi Sad number contain no zone code — numbers from different cities share a tail. Separate such lines by hand.
6. Outbound calls are rejected or leave with a different number. The carrier only passes numbers from your contract: put your own number into "Show as", or leave it empty — the line number will be used.
7. Calls inside Serbia through Orion VoIP sound poor. That is by design: the carrier itself writes that such calls travel "via abroad" and does not recommend them. The service is not meant for receiving guest calls at all.

Causes that do not depend on the country are in "If calls do not go through"; the SIP trace in the trunk menu is described there too. Transport and codec requirements are in "Network and compatibility", outbound rules in "Outbound calls and Show as".

Frequently asked questions#

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

Two sensible options. SoftNET — a local carrier with its own SBC and IP authorisation: numbers in Belgrade, Novi Sad and Niš, a contract with a legal entity, weeks of lead time. Zadarma — an international provider: numbers in five Serbian cities plus 0800, connected within hours, and the paperwork is a company registration and an address. If you need a number in a specific city and would rather not negotiate with a carrier, the integrator Creomate does that for you.

My number is with mts or SBB. Can I connect it to our PBX?#

Not directly: their trunk arrives over the carrier's own channel with private addressing, while our PBX sits in the cloud. There are two ways out: take a second number from another provider and move guest calls onto it, or port the existing number — by law the procedure takes no more than one working day and is free for the subscriber.

Do I need a Serbian company to get a number?#

For a local carrier — practically yes: the contract is signed with a Serbian legal entity (APR extract, PIB) or with an individual holding an ID card. A foreign company without Serbian registration will find it easier to take a +381 number from an international provider, where the paperwork is a copy of the registration certificate and proof of address.

Why can I not simply buy a Belgrade number for a company with no office in Belgrade?#

Because the numbering plan ties a geographic number to a connection in that geographic zone, and sellers phrase this as an obligation to confirm physical presence in the city. An international provider will most likely issue the number, but put a real address into the form: if it is checked, you will be the one answering for it.

How many channels should I order?#

A channel is one simultaneous call, and in Serbia it is sold separately from numbers: with Telekom Srbija it is a separate contract item ("Trunking Call Capacity"), with Zadarma two lines come with the number and further ones are bought on top. A restaurant usually needs 2–4: one is taken by a guest, the second by a courier or a supplier.

Will a call to 112 work through a purchased trunk?#

Ask the carrier about it separately. Access to 112, 192, 193 and 194 is the service provider's statutory duty, but whether these calls pass through a subscriber SIP trunk is not publicly promised by Serbian carriers, and for Serbia DIDWW marks emergency calling as unavailable. Do not build the venue's emergency scenarios on PBX telephony.

Sources#

All links checked on 09.09.2026.

Carriers and providers

• SoftNET — Telefonija (SIP trunking, IP centrex, On site IP-PBX): https://www.softnet.rs/Telefonija/Telefonija_2/
• SoftNET — Zašto VoIP?: https://www.softnet.rs/Zasto_VoIP_1/
• Creomate — DID VoIP-trunks Srbija (trunk modes per carrier): https://creomate.rs/did-voip
• Creomate — 3CX Generic SIP trunk to SoftNET SBC: https://creomate.rs/softnet
• Orion telekom — SIP parameters for a softphone: https://voip.oriontelekom.rs/soft-phone.asp
• Orion telekom — Orion VoIP preko Interneta: https://voip.oriontelekom.rs/voip-preko-interneta.asp
• Orion telekom — FAQ: https://voip.oriontelekom.rs/faq.asp
• SAT-TRAKT — Fiksna telefonija za poslovne korisnike: https://www.sattrakt.rs/servisi/fiksna-telefonija-za-poslovne-korisnike/
• Telekom Srbija (mts) — Business Trunking: https://mts.rs/Poslovni/Fiksna/Biz-linije/Business-trunking
• Telekom Srbija (mts) — Cenovnik za fiksnu poslovnu liniju (PDF): https://mts.rs/Binary/973/Cenovnik-za-Fiksnu-poslovnu-liniju.pdf
• SBB — SIP Trunk: https://poslovni.sbb.rs/telefonija/sip-trunk/
• SBB — IP Centrex: https://poslovni.sbb.rs/telefonija/ip-centrex/
• A1 Srbija — Poslovni: https://a1.rs/poslovni
• Yettel Srbija: https://www.yettel.rs/
• BeotelNet — Fiksna telefonija za poslovne korisnike: https://www.beotel.net/poslovni/fiksna-telefonija
• Cloud PBX (IPHouse): https://cloudpbx.rs/sr
• HostArena — HA Cloud PBX: https://hostarena.rs/ha-cloud-pbx/
• SkyTel Srbija: https://skytelsrbija.com/
• Zadarma — Serbian numbers: https://zadarma.com/en/tariffs/numbers/serbia/
• DIDWW — Serbia Toll Free: https://didww.com/phone-numbers/all-phone-numbers/Serbia/Toll_Free
• CommPeak — SIP Trunking Serbia: https://www.commpeak.com/services/sip-trunking/serbia
• PBX.IM — SIP Trunking Serbia: https://www.pbx.im/services/sip-trunking-provider/rs
• Sonetel — Virtual Phone number in Serbia: https://sonetel.com/en/help/help-topics/telephony/countries-supported/virtual-phone-number-in-serbia/

Regulator and legislation

• RATEL — Numeracija: https://www.ratel.rs/sr/numeracija
• RATEL — Standardna ponuda za uslugu terminacije poziva u fiksnoj mreži Telekom Srbija (codecs, transport, DTMF, PDF): https://www.ratel.rs/uploads/documents/empire_plugin/Standardna%20ponuda%20za%20uslugu%20terminacije%20poziva%20u%20fiksnoj%20mrezi%20Telekom%20Srbija%20april%202021.pdf
• Pravilnik o utvrđivanju plana numeracije ("Sl. glasnik RS" 44/2025, 64/2025): https://www.paragraf.rs/propisi/pravilnik-o-utvrdjivanju-plana-numeracije.html
• Zakon o elektronskim komunikacijama ("Sl. glasnik RS" 35/2023): https://www.paragraf.rs/propisi/zakon-o-elektronskim-komunikacijama.html
• Zakon o zaštiti podataka o ličnosti ("Sl. glasnik RS" 87/2018): https://www.paragraf.rs/propisi/zakon_o_zastiti_podataka_o_licnosti.html

The subscriber trunk settings of Telekom Srbija and SBB quoted on this page (the private addresses 10.0.0.2, 10.10.8.4, 10.248.0.17, the login format, the registration mode) are not published by the carriers themselves — they are known from the accounts of integrators who connected those trunks and are given here as a warning, not as ready-to-use parameters. Verify them against the carrier's settings sheet before signing.

Related pages#

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