VAPI•6mo ago

Issue to transfer call from VAPI to GoTo with extension

Hi Guys, I'm having an issue with call transfers when I need to have the AI dial an extension. We currently have this setup however our customer's phone system doesn't recognize this in the same way as a human dialing the extension and thus the call recipient's Voice Mail never kicks in. Have you guys come across this issue before? Do you have any insight as to how we can trouble shoot this?

These people with the GoTo system for some reason when VAPI AI makes the transfer to the person at their extension, their phone will ring but for some reason their voicemail never kicks in. I’ve tested this many times today. VAPI making the transfer vs. My calling in their direct line and pressing their extension manually, in that case their voicemail will kick in.

organizationid: 07c645bc-b098-43c4-b631-7fc5fae7d0c5
assistantid: cfe7d417-58ef-4487-84e7-a69696c2be96
callid: a8d46633-1bf4-432d-9510-a1ace7cad621

VapiAPP•7/13/25, 12:08 AM

Hey Seygi,

Thank you for reaching out. Please note that our team does not operate over the weekend. We'll be back in the office on Monday and will dive straight into your issue then to determine the best way forward.

Ccomprehensive-tomato Hey Seygi, Thank you for reaching out. Please note that our team does not opera...

broad-salmonOP•7/14/25, 5:23 PM

sure, tks

VapiAPP•7/15/25, 5:06 PM

Try switching from sipVerb: "refer" to sipVerb: "bye" and use the extension field separately instead of embedding it in the number. Also, adjust voicemail detection timing settings in vapi..

Ccomprehensive-tomato Try switching from sipVerb: "refer" to sipVerb: "bye" and use the extension fiel...

broad-salmonOP•7/16/25, 1:53 PM

How can I use the extension separately? do you have a transfertool payload with this example?

VapiAPP•7/16/25, 11:45 PM

Hey Seygi,

I wanted to let you know that we're managing a high volume of support requests at
the moment, so our response time might be a bit slower than usual.
I truly appreciate your understanding and will get back to you as soon as possible!

Thanks again for your patience!

Ccomprehensive-tomato Hey Seygi, I wanted to let you know that we're managing a high volume of supp...

broad-salmonOP•7/17/25, 9:38 AM

Okay

VapiAPP•7/19/25, 4:12 AM

If there is a message said by an automated machine before you need to enter the extension, use that message in your assistant prompt as the cue to call a tool that returns the keypad entry for the extension number.

Ccomprehensive-tomato If there is a message said by an automated machine before you need to enter the ...

broad-salmonOP•7/22/25, 2:16 AM

But the call transfer tool already has this option, to add the extension

VapiAPP•7/23/25, 9:46 AM

Yes, but if you are experiencing issues with that function for this scenario we should consider some alternatives. For example, we have a DTMF tool that you can configure to have your assistant dial a sequence of numbers on a keypad to trigger the dial tone frequency. The tool configuration would look something like this:

// POST /tool
{
  "type": "dtmf",
  "function": {
    "name": "dialExtension", // optional, defaults to "dtmf"
    "description": "Dial an extension or sequence of numbers on the keypad", // optional
    "parameters": {
      "type": "object",
      "properties": {
        "keys": {
          "type": "string",
          "description": "The key or sequence of keys to dial on the keypad. 1-9, *, #. They can optionally be combined. For example, 1234*"
        }
      },
      "required": ["keys"]
    }
  },
  "messages": [
    {
      "type": "request-start",
      "content": "I'll dial that extension for you now."
    },
    {
      "type": "request-complete", 
      "content": "Extension dialed successfully."
    }
  ]
}

// POST /tool
{
  "type": "dtmf",
  "function": {
    "name": "dialExtension", // optional, defaults to "dtmf"
    "description": "Dial an extension or sequence of numbers on the keypad", // optional
    "parameters": {
      "type": "object",
      "properties": {
        "keys": {
          "type": "string",
          "description": "The key or sequence of keys to dial on the keypad. 1-9, *, #. They can optionally be combined. For example, 1234*"
        }
      },
      "required": ["keys"]
    }
  },
  "messages": [
    {
      "type": "request-start",
      "content": "I'll dial that extension for you now."
    },
    {
      "type": "request-complete", 
      "content": "Extension dialed successfully."
    }
  ]
}

Then once you add this tool to your assistant, you write in the prompt "use the dtmf tool to dial an extension XXXX"

Ccomprehensive-tomato Yes, but if you are experiencing issues with that function for this scenario we ...

broad-salmonOP•7/23/25, 2:19 PM

But I need to do this during the transfer call, is it possible?

broad-salmonOP•7/25/25, 9:35 PM

@Shubham Bajaj could you support me?

broad-salmonOP•7/28/25, 7:36 PM

Hey team

I still need help with this issue.

Just to recap — this problem only occurs when the call goes to voicemail. If the destination operator answers the call, everything works fine.
The destination is a number + extension

I’ve tested the following transfer mode:
• blind-transfer
• warm-transfer-say-summary
• warm-transfer-wait-for-operator-to-speak-first-and-then-say-summary

Unfortunately, none of them resolved the issue.

Here are the details:
• assistantId: 627e5aaa-d438-4415-8466-2092e1d2b385
• callId: ee5ae789-e96b-43b2-9349-67ee32d1b8bb

Let me know what else I can provide to help debug this. Thanks!

broad-salmonOP•7/29/25, 2:10 PM

@Vapi Team

VapiAPP•7/30/25, 8:33 AM

We are reviewing the call id to see if there is any configuration that could be implemented for this scenario.

dangerous-fuchsia•7/31/25, 5:25 AM

@Seygi Can you please check your DM?

// POST /tool { "type": "dtmf", "function": { "name": "dialExtension", // optional, defaults to "dtmf" "description": "Dial an extension or sequence of numbers on the keypad", // optional "parameters": { "type": "object", "properties": { "keys": { "type": "string", "description": "The key or sequence of keys to dial on the keypad. 1-9, *, #. They can optionally be combined. For example, 1234*" } }, "required": ["keys"] } }, "messages": [ { "type": "request-start", "content": "I'll dial that extension for you now." }, { "type": "request-complete", "content": "Extension dialed successfully." } ] }

Issue to transfer call from VAPI to GoTo with extension

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