Since my last post about linking ElevenLabs and 3CX, there’s another setting that will make the integration experience better.

Passing through caller ID

By default, an outbound call via a SIP trunk in 3CX will pass through the outbound caller ID as defined in the trunk, extension or department. This doesn’t work for forwarding calls out of 3CX to your AI voice agent, so we’ll need to make some changes to the trunk to ElevenLabs.

Unfortunately, since 3CX version 20, it’s not so straight forward to simply update the outbound caller ID anymore, and instead requires exporting and re-importing the trunk config:

1. Export your SIP trunk from Voice & Chat (Click … -> Export)
2. Save the file as Provider.pv.xml and edit it in a text editor.
3. Find the section:
   <field name=”ParameterOut” custom=”” parameter=”FromUserPart”>$OutboundCallerId</field>
4. And update the value to:
   <field name=”ParameterOut” custom=”” parameter=”FromUserPart”>$OriginatorCallerId</field>
5. Save the file and import it back into 3CX: Admin -> Advanced -> Templates -> Provider Templates -> Import Provider
6. Setup your outbound rules as required.
   

Now when calls are passed through to ElevenLabs, you can add the caller ID as a variable (system__caller_id) to be used in your prompts and tools, as well as being stored in the agent logs. You might want to use the caller ID to call tools like looking up a customer in a CRM or sending a verification SMS.

• 3cx
• ai
• elevenlabs
• sip
• voice

• Bridging the Gap: Connecting 3CX to ElevenLabs AI Voice Agents for Next-Level Call Handling
  2025-07-05 1