Retell AI on a Jamaican Number: Import Your +1-876 Line via SIP Trunking with WOCOM

Retell AI is a platform for building voice agents that handle real phone calls: answering questions, booking appointments and qualifying leads. It supports custom telephony, so you keep your phone carrier and your number. For a Jamaica business that means your existing +1-876 line, carried by WOCOM, with a Retell agent answering.

What You Need

• A WOCOM number on Cloud PBX or a SIP trunk.
• A Retell AI account with an agent built and tested.
• From WOCOM: a termination URI (the address Retell sends outbound calls to) and a SIP username and password.

Step 1: Import the Number into Retell

1. In the Retell dashboard, open Phone Numbers → Add number → Import via SIP trunking.
2. Enter your number. E.164 form is safest: +1876XXXXXXX.
3. Enter the termination URI WOCOM gave you. Retell does not provide one of its own; outbound calls go wherever this field points.
4. Set Outbound Transport to TCP, which Retell recommends. UDP, TLS and mutual TLS are also available.
5. Fill in SIP Trunk User Name and SIP Trunk Password.
6. Click Test SIP Connection. Retell sends a SIP OPTIONS request to WOCOM. A 401 or 407 response means the credentials are wrong; a 403 means an IP address is not allowed yet.
7. Assign your agent to the number for inbound calls, outbound calls or both.

Step 2: Ask WOCOM to Route the Number

Send WOCOM support the following:

• The Jamaican number(s) you want answered by the AI, written in E.164 form (for example +1876XXXXXXX or +1658XXXXXXX).
• The platform's SIP address for inbound calls (shown below for this platform).
• Whether the AI also needs to place outbound calls, and from which number.
• Where calls should go if the AI hands a caller to a person: an extension, a ring group, or a mobile number.

For Retell, the inbound address is sip:sip.retellai.com, with transport added as needed, for example sip:sip.retellai.com;transport=tcp. Retell publishes the address ranges WOCOM should allow: 18.98.16.120/30 for signalling, plus 3.42.144.0/23 and 153.57.128.0/18. Some US traffic also comes from 143.223.88.0/21 and 161.115.160.0/19. Audio uses UDP ports 10000–65535.

Codecs and Encryption

Retell accepts PCMU, PCMA and G.722, all enabled by default, with 20 ms packets. It does not support Opus. If the two sides cannot agree on a codec, the call fails with a 488 error, but WOCOM supports both G.711 and G.722, so this should not happen. Encrypted audio (SRTP) requires TLS signalling and uses SDES key exchange. If you need it, ask WOCOM to enable TLS and SRTP on your route before you switch Retell to TLS.

Transfers

Retell supports cold transfers with SIP REFER: the agent hands the caller to a person and leaves the call. The target can be an extension on your Cloud PBX or a mobile number reached through WOCOM. REFER and onward calling must be allowed on your trunk, so mention transfers when you contact WOCOM. Retell agents also accept keypad input (DTMF).

Retell has a second option that does not need a trunk: you register each call through its API and dial sip:{call_id}@sip.retellai.com within five minutes. It is useful for experiments, but it does not support transfers. Use the trunk import for a real receptionist line.

What It Costs (November 2026)

At the time of writing, Retell charged about US$0.055 per minute for its voice engine, plus text-to-speech from about US$0.015 and the language model's rate. It charged nothing for custom telephony. That typically works out at US$0.07–0.31 per minute depending on the model, plus your WOCOM call charges. Retell offers models from OpenAI, Anthropic Claude and Google Gemini, as well as speech-to-speech options.

Retell or WOCOM AI?

Retell suits businesses that want a dashboard-driven builder with good testing tools and are willing to manage the agent themselves. WOCOM AI is included with Cloud PBX and is already set up for Jamaican callers, business hours and message taking. Read the overview of every platform, or contact WOCOM to get a termination URI and credentials for Retell.