We enabled VAPI voicemail detection on our product, but noticed that we're still getting billed for Twilio AMD. Is this expected behavior? If so, how can we ensure that Twilio AMD is disabled?

Enabling Vapi voicemail detection does not automatically disable Twilio AMD (Answering Machine Detection) or its billing. To avoid Twilio AMD charges, ensure that AMD is disabled in your Twilio trunk or number configuration. In your Twilio Console, check your SIP trunk or phone number settings and make sure AMD is turned off, as Vapi's detection will handle voicemail detection independently. Source: - [Vapi Voicemail Detection Documentation](https://docs.vapi.ai/calls/voicemail-detection)

Can you please provide a call id? We can investigate the logs and look at your assistant config

Here is a call ID for you:

5dfd76d0-bd0b-4960-a6e1-5c89a6a5440f

Looks like your assistant config is correct, just check on the twilio dashboard to make sure AMD is turned off.

We never enabled AMD manually in twilio, and the twilio docs mention that it's enabled per-request when sending the outbound call. Do you happen to know where we would disable this in the dashboard or verify that it's no longer being used? (note that I'm chiming in here because I'm part of the same dev team - I promise I'm not just drive-by sniping the thread 😅)

Here is the relevant documentation: https://www.twilio.com/docs/voice/answering-machine-detection#making-a-call-with-amd

Not sure where to disable in the dashboard, but via API you can make these changes

{
  "voicemailDetection": {
    "provider": "vapi",
    "enableTwilioBeepDetection": false
  }
}

Just tried your suggestion and unfortunately it doesn't work. It looks like the API doesn't allow us to set

enableTwilioBeepDetection

. Perhapse this property does not exist? https://cdn.discordapp.com/attachments/1381754951339872326/1383306596901322893/Screenshot_2025-06-14_at_12.44.24_AM.png?ex=684e5029&is=684cfea9&hm=37a43ca569ca7f6cd7c17f8bb6d17561b948bca073eb92f7337d5b80d52458f8&

Ah my mistake, it was a property that exists in the codebase but is unable to be modified via API endpoint. If you absolutely need AMD, VAPI AMD by default uses twilio as a fallback, but this snippet may disable the fallback while still keeping VAPI AMD:

{
  "voicemailDetection": {
    "provider": "vapi",
    "backoffPlan": {
      "startAtSeconds": 5,
      "frequencySeconds": 5,
      "maxRetries": 6
    }
  },
  "voicemailDetectionEnabled": false
}

@DonutDeflector Did you find a way to solve this?

@woody It seems like VAPI's voicemail detection method uses a hybrid approach, combining Twilio's machine beep detection and LLM analysis. So getting billed for Twilio beep detection is actually expected behavior.

Hey! I got this response too but something is not sitting right. If I didn't link my Twilio account how would this work, still awaiting a response.

Any service you use where you haven't linked an account for will be on your combined statement from Vapi directly.