On warm transfers, we need the original caller’s number to display on the destination handset. The ‘User’s Number’ option gets rejected by both Twilio and Telnyx because the caller’s number isn’t a verified DID. We also can’t set a Diversion header because custom headers are limited to X- prefixes. Is there a supported way to achieve caller ID passthrough on warm transfers?
This is currently only possible with numbers bought through the platform, the only other way would be sending sip headers if you have access to the receiving system.
Best,
Colin