I've been trying to configure this for the past 2 hours. For some reason I have warm-transfer-experimental set on my transferCall plan, the assistant says the transfer message to the customer but then ends the call. However on vapi side it shows the call was forwarded. Call IDs: eab3d3dc-3f67-4c98-9666-a56fae166498 8232e44c-ecfb-4522-95ba-1ef5d990fa6a Here is my setup { "type": "transferCall", "function": { "name": "myTransferCall" }, "destinations": [ { "type": "number", "number": "+1XXXXXXXXXX, "message": "Give me one moment to get an advisor on the line", "transferPlan": { "mode": "warm-transfer-experimental", "message": "Transferring a customer to you.", "fallbackPlan": { "message": "Could not get an advisor, goodbye." }, "holdAudioUrl": "https://music.vapi.ai/waiting-ringtone.mp3" } } @Shubham Bajaj

Hey Vstar, thanks for sharing the call ID. I'm currently busy with some ongoing work, so I apologize for not being able to look into your issue right away. Please give me some time to get back to you.

Hey @Shubham Bajaj thank you very very much!

Hey @vstar, the warm transfer experiment only works with Twilio-based calls, so that's why it's failing for your calls. As of now, we cannot extend the support for other telephony providers. The reason is that each telephony provider has its own markup language, and it's not feasible currently to create one solution that works for all of them. I hope you understand.

@Shubham Bajaj gotcha. So which transfer method would work with Twilio SIP Trunks?

All of the warm transfer method supports Twilio.

@Shubham Bajaj So the calls are initiated with Twilio SIP trunks, even the ones call IDs I listed that the assistant would just hang up the call.

Hey Vstar! Thanks for sharing the call id. Let me go through it and then get back to you.

cc798167-9947-45cf-8fad-89b1165e12c8

Hey @vstar, Based on my comprehensive log analysis of both call IDs, here's what I found: **Call ID eab3d3dc-3f67-4c98-9666-a56fae166498**: The transfer used blind-transfer mode (not warm-transfer-experimental as claimed), executed successfully with tool result "Success," and ended with assistant-forwarded-call status. **Call ID 1364018b-b101-4a5a-b13b-6ebba2df296a**: The transfer used warm-transfer-say-message mode, executed successfully, and also ended with assistant-forwarded-call status. In both cases, the logs show customers disconnected during the transfer process, which the system correctly detected and ignored since transfers were in progress.

Quick question @Shubham Bajaj, will the warm transfer with summary not work if the agent is using the free VAPI Number? The VAPI number is a Twilio based number right?

VAPI numbers are backed by some other providers, and as of now, warm-transfers only work with Twilio-based numbers.