Can't transfer to human

moderate-tomato · 2025-11-24T13:06:16.076Z

Whenever I try to transfer the call I am getting the "Call.in progress.error" transfer failed. I use Twilio for the phone number with IRELAND server location as I am based in Europe. Call ID: 019ab5d9-7ce2-755b-a0ef-8dea4bb7a1fb

V

Vapi Support BotAPP•11/24/25, 1:07 PM

Thank you for sharing the details. To help troubleshoot the "Call.in progress.error" transfer failure, could you confirm if your "transfer_call_tool" configuration includes the required "destination" parameter (the phone number to transfer to, in E.164 format)? Missing this parameter is a common cause of transfer issues according to the documentation.

If possible, please check your tool's parameters and let me know if the "destination" is set up correctly.

Sources:

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

M

moderate-tomatoOP•11/24/25, 1:10 PM

It looks correct to me @Vapi Support Bot

V

Vapi Support BotAPP•11/24/25, 1:11 PM

Thank you for confirming your configuration. Could you check if your assistant's configuration includes
"serverMessages": ["phone-call-control"]
"serverMessages": ["phone-call-control"]
"serverMessages": ["phone-call-control"]
"serverMessages": ["phone-call-control"] or if
phoneCallProviderBypassEnabled
phoneCallProviderBypassEnabled
phoneCallProviderBypassEnabled
phoneCallProviderBypassEnabled is set to
true
true
? These settings can override Vapi's call control and cause transfer failures, according to the documentation. Let me know what you find so we can proceed.

Source:

Debug call forwarding drops

M

moderate-tomatoOP•11/24/25, 1:18 PM

There is no such thing as "serverMessages" or "Phone-call-control" or "phoneCallproviderbypassenabled" in my assistants configuration JSON, But I am also NOT able to edit it as I am in the web interface dashboard @Vapi Support Bot

V

Vapi Support BotAPP•11/24/25, 1:19 PM

Thank you for the update. To help narrow down the cause, could you please check the "endedReason" for your failed call (ID: 019ab5d9-7ce2-755b-a0ef-8dea4bb7a1fb) in the Vapi dashboard or via the API? This value will indicate whether the transfer was initiated or blocked by configuration, which is a key step in troubleshooting according to the documentation.

If you can share the "endedReason" value, I can guide you on the next steps!

Source:

Debug call forwarding drops

M

moderate-tomatoOP•11/24/25, 1:21 PM

Ended: Call.in progress.error transfer failed @Vapi Support Bot

V

Vapi Support BotAPP•11/24/25, 1:22 PM

Suggestion:
Please double-check that your transfer destination number is in the correct E.164 format (e.g.,

+35312345678

+35312345678

+35312345678

+35312345678 for Ireland). Try calling this number directly from your phone to ensure it is reachable.

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+35312345678"], // Replace with your actual number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+35312345678"], // Replace with your actual number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+35312345678"], // Replace with your actual number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+35312345678"], // Replace with your actual number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

If the number is correct and reachable, review your Twilio call logs for any transfer errors.
Source: Debug call forwarding drops

M

moderate-tomatoOP•11/24/25, 1:24 PM

{
"id": "58bc5653-f8c6-4450-b6d9-61b1cbb4350b",
"createdAt": "2025-10-19T17:59:36.705Z",
"updatedAt": "2025-11-24T13:09:08.656Z",
"type": "transferCall",
"function": {
"name": "transfer_call_tool"
},
"messages": [
{
"type": "request-start",
"content": "",
"blocking": false
}
],
"orgId": "117c82dd-62c3-421e-9e72-2a31d32a1a12",
"destinations": [
{
"type": "number",
"number": "+49173REDACTED",
"message": "Einen Moment, ich werde Sie weiterleiten.",
"callerId": "REDACTED",
"description": "When they want to speak with "REDACTED" you will forward",
"transferPlan": {
"mode": "blind-transfer",
"sipVerb": "refer"
},
"numberE164CheckEnabled": true
}
]
}

@Vapi Support Bot

V

Vapi Support BotAPP•11/24/25, 1:25 PM

Next step:
Check your Twilio Console call logs for the failed transfer. Go to Twilio Console > Call Logs, search for the call using the

phoneCallProviderId

phoneCallProviderId

(e.g.,

CAabc123

CAabc123

CAabc123

CAabc123), and look for transfer-related errors in the call timeline. This will help pinpoint if Twilio rejected the SIP REFER or if there’s a provider-side issue.
Source: Debug call forwarding drops

M

moderate-tomatoOP•11/24/25, 1:37 PM

This is my log @Vapi Support Bot

message.txt138.77KB

M

moderate-tomatoOP•11/24/25, 1:43 PM

@Vapi Team

M

moderate-tomatoOP•11/24/25, 1:43 PM

@Vapi Support Bot did you see the logs?

M

moderate-tomatoOP•11/24/25, 1:45 PM

Fixed it as I changed twilio routing to US

A

awake-maroon•11/24/25, 2:54 PM

hey @DNP i am having a similar issue where we are paying for the transfer minutes after the transfer, are you seeing similar with twilio?

A

awake-maroon•11/24/25, 2:54 PM

right now we are using a telephony connected number to transfer

K

KyleAPP•11/26/25, 5:25 PM

Hi DNP,

If you encounter issues while using the transfer tool, it might help to ensure that the correct transfer destination type is being used (

TransferDestinationNumber

TransferDestinationNumber

TransferDestinationNumber

TransferDestinationNumber or

TransferDestinationSip

TransferDestinationSip

TransferDestinationSip

TransferDestinationSip). Additionally, check if the

transferPlan

transferPlan

transferPlan

transferPlan has the appropriate

mode

mode

mode

mode and if the

message

message

or

sipUri

sipUri

sipUri

sipUri fields are correctly configured.

If you're experiencing server errors or call failures during the transfer, refer to this document for detailed error codes and messages. This can help troubleshoot whether the issue is related to quota limits, authentication, or anything else specified in the error descriptions.

For creating a transfer tool or checking configurations, the definitions and required fields for creating a tool can be found in the tool creation API documentation.

If the problem persists, please check your setup against the documentation to ensure all parameters are correctly used.

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Can't transfer to human

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