Turkey: SIP providers and connecting a number to the PBX

This page continues the general guide on connecting a provider's number to the PBX, which covers everything that is the same for any carrier (the two trunk modes, what to ask for, what to enter in the form, network and testing). Here is the Turkish specifics: who in the country sells a number with a SIP trunk, what exactly that carrier issues, and what of it goes into Telephony → "Trunks and connections" → "Add provider".

In short#

• Numbers in Turkey are issued by carriers holding an STH authorisation (Sabit Telefon Hizmeti). Not all of them give a trunk to your PBX over the ordinary internet: parameters are published only by Verimor and Netgsm, the rest hand them over under a contract.
• Verimor Telekom — registration mode (REGISTER) on sip.verimor.com.tr; it is the only carrier in the country with an open Asterisk/FreePBX guide.
• Netgsm — REGISTER on sip.netgsm.com.tr, plus a "SIP Trunk" switch in the account panel that sends incoming calls straight to your PBX IP address. In other words, both of our modes work with it at once.
• The main local pitfall: Türk Telekom, Turkcell Superonline and Vodafone sell a SIP trunk only on top of their own access line at the customer's premises. A cloud PBX cannot be connected to such a trunk at all — see the section below.
• The paperwork is Turkish and on paper: a subscriber contract, an ID document, imza sirküleri, vergi levhası, a yerleşim yeri belgesi from e-Devlet. In practice a Turkish legal entity is required.
• ⚠️ Today a dedicated PBX is not created for locations in Turkey: receiving calls on your own switch here requires an authorisation from the communications regulator (BTK), and without it providing the service is a criminal offence. This guide will be useful once a launch becomes possible — and it already helps you pick a carrier and a number.

Numbers in Turkey#

• Country code +90. The national format is 0 plus 10 digits: three digits of the area or carrier code and seven digits of the subscriber number.
• Geographic numbers start with 2, 3 and 4: 212 Istanbul (European side), 216 Istanbul (Asian side), 312 Ankara, 232 Izmir, 224 Bursa, 242 Antalya, 322 Adana, 332 Konya, 342 Gaziantep.
• 0850 is a number not tied to a city (konumdan bağımsız): the workhorse of cloud PBXs, the caller pays as for a local call. 0800 is toll-free for the caller, 444 plus 4 digits is a short corporate number valid across the country, 5xx are mobile numbers.
• In the carrier's account panel the number is usually shown in the national form (0850 XXX XX XX, 0212 XXX XX XX), while a call may arrive either that way or as +90…. For the "Lines" tab this does not matter: the PBX compares the last seven digits, and that is exactly the Turkish subscriber number.

Who issues a number with a SIP trunk#

Verimor Telekom#

An STH carrier selling voice services (0850, geographic, 444 and foreign DID numbers), a cloud PBX and SMS. What you need is not their cloud switch but the basic "IP arabağlantı" (SIP Trunk) service: the carrier describes it precisely as the simplest way to give an external line to your own IP PBX — no hardware and no hard channel limit. To connect, file a subscription application or call the sales department, then submit the documents (see "Rules and paperwork").

What to enter in the admin panel

The port and the transport are not stated explicitly in the carrier's guide: these are the standard values, confirm them when connecting.

What to set up at the provider

• sign the subscriber contract and obtain a SIP account;
• order a number (0850 or geographic) or port an existing one;
• ask for the right to display that number as the outbound CallerID: without the carrier's permission the "Display as" field will not work;
• make sure the alaw/ulaw codecs are allowed on the trunk;
• check how many simultaneous calls are included in the tariff.

⚠️ Verimor's codec set includes G.729, which the PBX does not understand. The carrier also offers G.711, so the pairing does work — but insist on alaw/ulaw when agreeing the setup, otherwise you may end up with "the call connects but there is no sound". And do not mix things up: the "SIP Trunk" module of their cloud PBX is the opposite direction (collecting other carriers' numbers into their cloud), not a line out.

Source: Verimor, FreePBX Trunk Ayarları (09.09.2026).

Netgsm#

A large carrier: landline telephony, mobile service, SMS and a cloud PBX. For an external switch it offers two different things, and they should not be confused:

1. The SIP account of the number — in the account panel, Ses Hizmeti → Ayarlar → SIP Bilgileri: server address, user name and password. This is an ordinary trunk with registration.
2. The "SIP Trunk" switch — in the same place you enter the IP address or domain of your server and the port to which Netgsm will send incoming calls, plus the "Arayan Prefix" and "Aranan Prefix" settings (in which form the caller's number and your number will arrive). This is IP authorisation on the inbound leg.

What to enter in the admin panel

What to set up at the provider

• in Ses Hizmeti → Ayarlar → SIP Bilgileri enable "SIP Trunk" and enter the static IP of your PBX (the "Server" tab in the Telephony section) and port 5060;
• set "Aranan Prefix" so that the number arrives in a predictable form (+90… or national) and save the SIP trunk settings with the save button;
• point the purchased number at this SIP account.

⚠️ Netgsm does not publish its codecs or its DTMF method — ask the carrier whether G.711 alaw/ulaw is allowed on the trunk before promising the venue a working number. The address sip.netgsm.com.tr appears only inside integration articles: the carrier has no dedicated "SIP parameters" page, so you will not notice an address change immediately.

Source: Netgsm, forwarding incoming calls to your server and the SIP parameters in the integration guide (09.09.2026).

Telsam Telekom#

An STH carrier: landline telephony, 0850 and geographic numbers, a cloud PBX, a call centre and SMS. Publicly it documents only the extensions of its own switch (guides for softphones and desk phones). The minimum working option is therefore to register your PBX as an extension of the carrier and point the number at it; a full trunk with several numbers has to be requested from the sales department separately.

What to enter in the admin panel

The carrier does not publish the port and the transport — these are the standard values, confirm them in the account panel.

What to set up at the provider

• create an extension (or ask for a full trunk) and find out the IP address of the switch;
• point the purchased number at this extension;
• request the right to display the number as the outbound CallerID.

⚠️ The switch address is an IP address, not a name: if the carrier moves, the trunk dies silently and the PBX stops recognising its incoming calls. Besides, the "PBX as an extension" scheme gives you one line: the call will carry the login instead of the number — how to deal with that is described in step 3 of the overview.

Source: Telsam, registration parameters (09.09.2026).

Contract-only providers#

These carriers do have a trunk for a third-party IP PBX, but they publish neither the host nor the authorisation mode: the parameters are handed over by an account manager after the contract. What exactly to ask for is the list in "What to ask the provider"; in addition, have the static IP of your PBX ready (the "Server" tab) — it will be needed for the allowlist.

• KobiKom Telekomünikasyon — an STH carrier with the full range of number services (0850, 0800, landlines in 81 provinces, porting). Its "SIP Trunk & DID" service is described exactly as needed: it connects the customer's existing IP PBX to the carrier network over the ordinary internet, the number of channels is set in software, dozens of numbers can share one trunk. G.711 and G.729 are advertised — ask for alaw/ulaw. Signalling encryption is an option for them, not an obligation, so a plain UDP trunk goes through. It starts with a free "capacity analysis".
• CloudCell — corporate connectivity for legal entities: "Kurumsal Sabit Telefon ve SIP Trunk", capacity measured in simultaneous channels, numbers assigned or ported, separate permissions for incoming and outgoing calls. This is a contracted service with support and monitoring, not a five-minute self-service signup.
• 3c1B Telekom — an Ankara carrier (internet access, data centre, wholesale voice, the "STH / Toptan" section). One of the two Turkish providers whose trunk has been tested by the 3CX vendor, which means connecting a third-party IP PBX is well trodden there. There is no retail self-service, everything goes through a quote.
• Avencom Telekom — a carrier operating since 2010, holding both regulator authorisations (STH and internet service provider), assigning and porting landline numbers, with public per-minute rates. The second provider from the 3CX list. There is no technical documentation at all — only the sales department and application forms.
• Alltel and Bulutfon — carriers with their own cloud PBXs and numbers; a trunk to an outside switch is not offered as a separate product. If you want to work with them specifically, ask the salesperson directly: "do you provide a SIP trunk to our own PBX in the cloud?"

The big three: why their trunk will not fit#

The three largest carriers do have a SIP trunk, and it is named almost the way you would want, but it is built differently: the voice travels over their own access line to your premises, and the trunk terminates on a switch standing right there.

• Türk Telekom, "IP Çoklu Hat" — the voice is packetised in the carrier network and delivered over its broadband line to a switch at the customer's premises; channels are sold in bundles and access redundancy is available.
• Turkcell Superonline, "Kurumsal VOIP" — the backbone runs over SIP, but the customer connects through an analogue, PRI or IP gateway or a router at their own site. The "SIP Trunk" feature of their "Akıllı Santral" gives the customer's existing switch limited access to their cloud, not a line out.
• Vodafone Business Türkiye — corporate VoIP in a "closed loop" over its own network (fibre, metro ethernet, corporate DSL). Their cloud PBX is designed for SIP phones, not for someone else's switch.

Our PBX lives in the cloud and has only a public static IP address — such a trunk cannot be pointed at it. This is the architecture of the service, not a tariff detail: there is no point arguing with the account manager, take a carrier from the sections above.

International providers with Turkish numbers#

A Turkish landline number can also be bought from an international service — then the trunk is theirs, and the parameters come from the provider card in the admin panel catalogue (see step 1 of the overview).

• Zadarma — Turkish numbers are sold online: 0800, Istanbul 0212 and 0216, Ankara 0312, Antalya 0242, Bursa 0224. Every number gives two lines, more are available for an extra fee. Documents: a company registration certificate and a letter requesting the number, or an ID document, plus an address in the same region where the number is ordered. ⚠️ An important restriction from Zadarma itself: Turkish virtual numbers are not intended for outbound calls within Turkey — they are fine for incoming calls, while outbound traffic has to be bought from a local carrier.
• DIDWW and AVOXI — both advertise Turkish landline numbers (Istanbul 212/216, Ankara 312, Izmir 232, Bursa 224, Antalya 242) delivered over SIP; the document requirements are the same — a legal entity and an address in the region of the number.
• Twilio — Turkey is present in its address requirements for numbers: an address matching the area code and supporting documents are needed; the availability of a particular city is checked by searching in the console.
• Telnyx — as of 09.09.2026 there are no Turkish numbers in its catalogue; its country-by-country DID requirements summary does not include Turkey.

Number porting#

• Porting is governed by a dedicated number portability regulation; for fixed numbers the mechanism has been operating since 2009. The initiator is the receiving carrier: you file an application with it (in writing, through the call centre or online), and it passes the request and the desired porting time to the portability system.
• Both a landline number and an 0850 number can be ported — every Turkish STH carrier in the table above sells "Numara Taşıma" as a separate service. The set of documents is the same as for a new connection.
• The exact timing and the switchover window depend on the carrier — ask when filing the application.
• Where a number is currently ported to can be checked with the regulator's "Taşınmış Numara Sorgulama" service on the BTK website.
• Pitfalls: a number registered to a private individual will additionally require a change of subscriber when ported to a company — a separate procedure with its own documents; 444 numbers are not geographic and follow their own rules.

Rules and paperwork#

Telecommunication services in Turkey may be provided only with an authorisation from the regulator (BTK), and operating without a right of use carries criminal liability under the law — which is exactly why the PBX is not yet enabled for Turkish locations. For a subscriber this only means that the number must be bought from an authorised carrier; below is what it will ask for.

If it does not work#

The general symptoms and their analysis are in the overview table. The Turkish specifics:

1. The call connects but there is silence. Verimor and KobiKom have G.729 in their codec set, and the PBX does not understand it. Ask the carrier to leave only G.711 alaw/ulaw on the trunk.
2. No incoming calls even though registration is green (Netgsm). Registration is responsible for outbound calls; incoming calls are sent by the carrier to whatever is set in the "SIP Trunk" switch. Check that the static IP of your PBX and port 5060 are entered there.
3. Everything suddenly broke (Telsam). Their switch address is an IP address, and it may have changed. Take the new one from the "dahili bilgileri" section of the account panel and update the SIP host field.
4. A carrier from the big three cannot point the trunk at your address. And it will not be able to: its trunk terminates on the access line at the premises — see the section above.
5. Outbound calls are rejected with an authorisation error. Turkish carriers grant the right to display a number as CallerID separately. Leave the "Display as" field empty and ask the carrier to enable that right for your numbers.
6. Calls to one Istanbul number land in another number's rule. The last seven digits of 0212 and 0216 numbers may coincide, and the PBX compares exactly those. Put such numbers on separate trunks.

Frequently asked questions#

Can a Turkish number be connected if the company is registered outside Turkey?#

With a local carrier — hardly: it asks for a tax certificate, signature specimens and an e-Devlet certificate, and those are Turkish documents. The realistic path without a Turkish legal entity is to buy a Turkish landline number from an international provider, but mind the restrictions on outbound calls within the country.

Which is better to take — a geographic number or 0850?#

An 0850 number is not tied to a city: it is equally convenient when a chain has venues in different cities, and the caller pays as for a local call. A geographic number looks "local" to guests of the neighbourhood — take it if there is a single venue and the city association matters.

Why not simply take a SIP trunk from Türk Telekom?#

Their trunk arrives over their own access line to a switch on your premises. Our PBX stands in the cloud and only has a public static address, and the carrier technically cannot point such a trunk at it. You need a carrier that works over the open internet.

Netgsm asks for the server IP and port — where do I get them?#

On the "Server" tab of the Telephony section: the "Static IP" field is the address of your PBX, the port is 5060 and the transport is UDP. The same address will be needed by any carrier that keeps an allowlist.

When will it be possible to connect the PBX for a venue in Turkey?#

As long as receiving calls on your own switch requires an authorisation from the local regulator, a dedicated PBX is not created for Turkish locations. The number and the carrier can be chosen already now: the Verimor and Netgsm parameters are exactly the ones that go into the provider form once a launch becomes possible.

Sources#

Links verified on 09.09.2026.

• Verimor — FreePBX Trunk Ayarları — trunk parameters for Asterisk/FreePBX.
• Verimor — documents required for a subscription — the subscriber document set.
• Netgsm — forwarding incoming calls to your server — the "SIP Trunk" switch and the prefixes.
• Netgsm — SIP parameters in the integration guide — server address, port, where to take the login and the password.
• Telsam — registration parameters — the switch address and the extension credentials.
• KobiKom — SIP Trunk and DID — a trunk over the internet, codecs, numbers.
• CloudCell — Kurumsal Sabit Telefon ve SIP Trunk — the corporate trunk.
• Türk Telekom — IP Çoklu Hat — binding to the access line, channels and prices.
• Turkcell Superonline — Kurumsal VOIP — connection through a gateway on the premises.
• Vodafone Business — Kurumsal VoIP — the carrier's closed loop.
• BTK — geographic numbers and 850 numbers — numbering and area codes.
• Law 5809 on electronic communications — authorisation of carriers and liability.
• Number portability regulation — the porting procedure.
• Zadarma — Turkish numbers — cities, documents, the outbound restriction.
• 3CX — Turkish providers tested by the vendor — 3c1B and Avencom.

Related pages#

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