One of our customers is facing call forwarding issues. The calls 1. a7d5f586-de2c-4106-9a1a-90a5a3b69786 2. a833bdc1-d0b8-45b2-a101-53861911eaba Both ended in a call.in-progress.error-transfer-failed error. The forwarding logic worked up until now and no changes were made to the assistants, so we can rule out potential errors like malformed destination numbers etc. We are using Twilio for the assistants phone number and within Console → Monitor → Calls → Error Logs no errors show up

Suggestion: Test your

transfer-destination-request

webhook endpoint directly to ensure it is reachable and returns a valid response. You can use the following sample payload to simulate a transfer request:

json
{
  "type": "transfer-destination-request",
  "call": { "id": "test-call-id", "status": "ongoing" },
  "phoneNumber": "+14155552671"
}

Respond with a valid destination object as shown in the [Vapi docs](https://docs.vapi.ai/calls/call-dynamic-transfers#respond-to-transfer-requests). This will help isolate whether the issue is with the webhook/server or elsewhere in the transfer flow. Source: - [Dynamic Call Transfers Vapi Documentation](https://docs.vapi.ai/calls/call-dynamic-transfers#respond-to-transfer-requests)

We are seeing these errors for both calls in our logs:

🟡 09:31:13:489 [twilioStream:0918e81d] Couldn't Transfer Twilio Call. Error: The requested resource /2010-04-01/Accounts/ACc65823f6e7e0aaa4bbe8412a59027485/Calls/CA3b4a26b8eaa5a02e79793ae3b0019642.json was not found

Please check with Twilio support for this specific error.

Thanks for the info. We had recently migrated the numbers from Twilio region US1 to IE1 due to regulatory compliance reasons. The Twilio team came back to us with the fix that the correct region needs to get addressed when handling the forwarding:

https://ie1.api.twilio.com

In the Vapi dashboard there is an option for "Server URL" but this doesn't seem to be the correct spot. Where can we set the corrent Twilio region?

Usually this is configured within Twilio itself. There should be a region setting for your specific phone number or account that will allow this change

Yes and the region is set to IE1 But it looks like Vapi is triggering a US1 endpoint when it tries to forward a call. The result is, that this (US-)endpoint doesn't find the number (because it now resides in IE1) and therefor throws an error. The end result is that the assisant wants to forward the call, Vapi triggers the wrong endpoint and the call gets hung up because the destination is not reachable

This change will most likely need backend modifications. We will check what this requires and get back to you

Okay great, thanks! Especially from a European compliance perspective, it’s important that companies operate their Twilio numbers within the IE1 region. If our assumption is correct and Vapi currently targets the US1 endpoint, it would be ideal to introduce a region switcher (US1 / IE1). A simple dropdown on the phone number details page (https://dashboard.vapi.ai/phone-numbers/) should do the trick to define where each number is managed.

We apologize for the delay in responses lately. We are in process of making some changes to our workflow in how we handle support requests. The good news is that we are starting to get back on track of having a 48 hour response time and we would like to start cleaning up anything old. With that being said, just wanted to check in with you to see if you have made any progress or changes to your project since support has last reached out.

@Henning you never found a solution to this? Dealing with the same thing