Connecting a virtual number to the Retell AI service

Retell AI – is a service that uses artificial intelligence to create voice agents capable of receiving and making calls.

The main advantages are the natural sound of neural network voices, quick integration, and support for multiple languages.

1. Setting up outgoing calls in Retell AI

In Retell AI go to the section "Phone Numbers", click the button "+" and select "Connect to your number via SIP trunking".

Enter the following parameters

• Phone Number – Your virtual number from your personal account
• Termination URI – sip.zadarma.com – server address for connection
• SIP Trunk User Name – Your SIP number from your personal account
• SIP Trunk Password – Your SIP number password which can be generated here
• Nickname – Your SIP number.

Click "Save".

Then, in the settings Inbound call agent и Outbound call agent select your voice agent. If the agent has not been created yet, create it in the Agents section.

The connection setup is complete. To make an outgoing call, click "Make an outbound call" and enter the number in international format with a +.

2. Incoming call reception setup in Zadarma.

To receive incoming calls, set up call forwarding from your Zadarma virtual number to Retell AI:

1. Go to the Zadarma section "Settings" → "Virtual phone numbers".
2. Next to your number, click on the ⚙ (gear) icon.
3. Open the tab "External server".
4. Enable the option "External server (SIP URI)".
5. In the field that appears, enter the address: +442045770077@5t4n6j0wnrl.sip.livekit.cloud, where +442045770077 – is your virtual number in international format.
6. Click "Save".

3. Additional settings in Retell AI

• Select the voice agent to which the number is connected.
• Specify whether the number will be used for incoming calls, outgoing calls, or both.
• Save the changes.

Your Zadarma virtual number is now fully integrated with Retell AI

Your voice agent can now receive and make calls.