I’m trying to integrate an external number to Telnyx for ‘TranferCall’. Issue I’m having, call fails each time it try’s to connect. I’ve configured SIP URL under destinations and added forwarding number as instructed. https://cdn.discordapp.com/attachments/1382996365151305738/1382996365365346385/Screenshot_2025-06-13_at_09.05.01.jpg?ex=684d2f3c&is=684bddbc&hm=5dc67a528291dc73c2bc3b8cc443bc840d5e51ef4ccafe94256c61b5c4e83ba2& https://cdn.discordapp.com/attachments/1382996365151305738/1382996365734318150/Screenshot_2025-06-13_at_09.04.14.jpg?ex=684d2f3c&is=684bddbc&hm=23bf8f06d378c53ccb42fac8b9ced653fbfb2ad6e3f63ebdfc1a7d88231f8adc&

Suggestion: Check that SIP REFER is enabled in your Telnyx SIP trunk settings—Vapi requires this for call transfers to work. If it's not enabled, contact Telnyx support to activate it. Also, ensure your destination SIP URI is formatted like this:

sip:+441234567890@sip.telnyx.com

Replace

+441234567890

with your actual external number in E.164 format. Sources: - [Vapi SIP Trunking Telnyx external number call forwarding troubleshooting](https://discord.com/channels/1211482211119796234/1343963959421829172) - [Vapi documentation: call forwarding](https://docs.vapi.ai/call-forwarding) - [Vapi SIP Trunking Guide](https://docs.vapi.ai/advanced/sip/sip-trunk)

FYI: SIF REFER has been enabled

Hi Dan, could you please share your call id for the call with the failed transfer?

Where do I locate call id? I’m out credits, could that be a reason?

Please review the attachment. If you go into the dashboard --> call logs it should be the first column https://cdn.discordapp.com/attachments/1382996365151305738/1383250941221928980/call_id.png?ex=684e1c53&is=684ccad3&hm=662cba91eea7159cb99995fdbbc02fc9d37d026e71180b4abcf5e99143f56ae6&