Unexpected Twilio Charges for Voicemail Detection Despite Using Vapi

elderly-tomato · 2025-10-13T09:50:52.916Z

Why is Twilio still charging me for voicemail detections when I’m not even using Twilio for that anymore, but Vapi instead? out of the 260 spent on twilio, 65 of it was only for voicemails...

V

Vapi Support BotAPP•10/13/25, 9:52 AM

To stop Twilio from charging for voicemail detection, you need to explicitly disable Twilio's Answering Machine Detection (AMD) in your Twilio call setup. Even if Vapi is set as your voicemail detection provider, Twilio will still charge for AMD if it's enabled in your Twilio configuration.

Here's how you can disable AMD in your Twilio API call:

// Example: Remove or set machineDetection to 'none' in your Twilio call
client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // <-- This disables AMD
});

// Example: Remove or set machineDetection to 'none' in your Twilio call
client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // <-- This disables AMD
});

// Example: Remove or set machineDetection to 'none' in your Twilio call
client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // <-- This disables AMD
});

// Example: Remove or set machineDetection to 'none' in your Twilio call
client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // <-- This disables AMD
});

Review your Twilio call flows and ensure "machineDetection" is not set or is set to "none" to avoid further charges.
For more details, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

⤵️ Mention @Vapi Support Bot for follow-ups 🐥

E

elderly-tomatoOP•10/13/25, 10:00 AM

where do I find the option to disable AMD

E

elderly-tomatoOP•10/13/25, 10:17 AM

@Duckie

V

Vapi Support BotAPP•10/13/25, 10:19 AM

To disable Twilio's Answering Machine Detection (AMD) and stop related charges, set the

machineDetection

machineDetection

machineDetection

machineDetection parameter to

'none'

'none'

'none'

'none' in your Twilio API call when creating outbound calls:

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

If you're using a UI or third-party tool, look for a setting labeled "Answering Machine Detection" or "AMD" and ensure it is turned off or set to "none".
For more details, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

E

elderly-tomatoOP•10/13/25, 10:19 AM

In my Twilio call logs, I’m seeing MachineDetection: "DetectMessageEnd" and AsyncAmd: true.

This means Twilio’s built-in Answering Machine Detection is still active and causing duplicate voicemail detection charges, even though Vapi is handling voicemail detection.

Please update my organization configuration so that machineDetection is set to 'none' when initiating Twilio calls.

Thanks!

E

elderly-tomatoOP•10/13/25, 10:20 AM

@Duckie

V

Vapi Support BotAPP•10/13/25, 10:20 AM

Based on the information you provided from your Twilio call logs—specifically seeing

MachineDetection: "DetectMessageEnd"

MachineDetection: "DetectMessageEnd"

MachineDetection: "DetectMessageEnd"

MachineDetection: "DetectMessageEnd" and

AsyncAmd: true

AsyncAmd: true

AsyncAmd: true

AsyncAmd: true—it does indicate that Twilio's built-in Answering Machine Detection (AMD) is still active. This is why you are continuing to see voicemail detection charges from Twilio, even though Vapi is handling voicemail detection on your end.

To prevent these duplicate charges, you need to ensure that the

machineDetection

machineDetection

machineDetection

machineDetection parameter is set to 'none' when initiating Twilio calls. This will disable Twilio's AMD and stop the extra charges for voicemail detection.

If you are using a custom integration or API, make sure your call creation code looks like this:

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

client.calls.create({
  to: TO_NUMBER,
  from: FROM_NUMBER,
  url: 'https://your-app.com/voice',
  machineDetection: 'none' // Disables AMD
});

If you are using a UI or third-party tool, look for a setting labeled "Answering Machine Detection" or "AMD" and ensure it is turned off or set to "none".

If you need to update your organization configuration, make sure that all outbound Twilio calls are set up with

machineDetection: 'none'

machineDetection: 'none'

machineDetection: 'none'

machineDetection: 'none' to avoid further charges.

Let me know if you have any other questions!

E

elderly-tomatoOP•10/13/25, 10:29 AM

currently this is how i trigger my calls right now
{
"assistantId": "fe970ff4-1ec0-4507-870f-5274b713625a",
"phoneNumberId": "0d63603b-4c45-47fc-b5fc-0244351ca7bf",
"customer": {
"number": "{{ $('Webhook').item.json.body.phone }}"
},
"assistantOverrides": {
"variableValues": {
"first_name": "{{ $('Webhook').item.json.body.first_name }}",
"Contact_ID": "{{ $('Webhook').item.json.body.contact_id }}",
"customer_email": "{{ $('Webhook').item.json.body.customData.customer_email }}",
"Address": "{{ $('Webhook').item.json.body.full_address }}",
"Service_Area": "{{ $('Webhook').item.json.body.customData['Service Area'] }}",
"conversation-summary": "{{ $json.conversation_summary }}"
}
}
}

is this where i should disable AMD? if yes how should it look like

@Vapi Support Bot

V

Vapi Support BotAPP•10/13/25, 10:31 AM

To disable Twilio's Answering Machine Detection (AMD) in your call trigger, add the

"machineDetection": "none"

"machineDetection": "none"

"machineDetection": "none"

"machineDetection": "none" field at the top level of your payload (if your integration supports passing this to Twilio). For example:

{
  "assistantId": "fe970ff4-1ec0-4507-870f-5274b713625a",
  "phoneNumberId": "0d63603b-4c45-47fc-b5fc-0244351ca7bf",
  "customer": {
    "number": "{{ $('Webhook').item.json.body.phone }}"
  },
  "machineDetection": "none",
  "assistantOverrides": {
    "variableValues": {
      "first_name": "{{ $('Webhook').item.json.body.first_name }}",
      "Contact_ID": "{{ $('Webhook').item.json.body.contact_id }}",
      "customer_email": "{{ $('Webhook').item.json.body.customData.customer_email }}",
      "Address": "{{ $('Webhook').item.json.body.full_address }}",
      "Service_Area": "{{ $('Webhook').item.json.body.customData['Service Area'] }}",
      "conversation-summary": "{{ $json.conversation_summary }}"
    }
  }
}

{
  "assistantId": "fe970ff4-1ec0-4507-870f-5274b713625a",
  "phoneNumberId": "0d63603b-4c45-47fc-b5fc-0244351ca7bf",
  "customer": {
    "number": "{{ $('Webhook').item.json.body.phone }}"
  },
  "machineDetection": "none",
  "assistantOverrides": {
    "variableValues": {
      "first_name": "{{ $('Webhook').item.json.body.first_name }}",
      "Contact_ID": "{{ $('Webhook').item.json.body.contact_id }}",
      "customer_email": "{{ $('Webhook').item.json.body.customData.customer_email }}",
      "Address": "{{ $('Webhook').item.json.body.full_address }}",
      "Service_Area": "{{ $('Webhook').item.json.body.customData['Service Area'] }}",
      "conversation-summary": "{{ $json.conversation_summary }}"
    }
  }
}

{
  "assistantId": "fe970ff4-1ec0-4507-870f-5274b713625a",
  "phoneNumberId": "0d63603b-4c45-47fc-b5fc-0244351ca7bf",
  "customer": {
    "number": "{{ $('Webhook').item.json.body.phone }}"
  },
  "machineDetection": "none",
  "assistantOverrides": {
    "variableValues": {
      "first_name": "{{ $('Webhook').item.json.body.first_name }}",
      "Contact_ID": "{{ $('Webhook').item.json.body.contact_id }}",
      "customer_email": "{{ $('Webhook').item.json.body.customData.customer_email }}",
      "Address": "{{ $('Webhook').item.json.body.full_address }}",
      "Service_Area": "{{ $('Webhook').item.json.body.customData['Service Area'] }}",
      "conversation-summary": "{{ $json.conversation_summary }}"
    }
  }
}

{
  "assistantId": "fe970ff4-1ec0-4507-870f-5274b713625a",
  "phoneNumberId": "0d63603b-4c45-47fc-b5fc-0244351ca7bf",
  "customer": {
    "number": "{{ $('Webhook').item.json.body.phone }}"
  },
  "machineDetection": "none",
  "assistantOverrides": {
    "variableValues": {
      "first_name": "{{ $('Webhook').item.json.body.first_name }}",
      "Contact_ID": "{{ $('Webhook').item.json.body.contact_id }}",
      "customer_email": "{{ $('Webhook').item.json.body.customData.customer_email }}",
      "Address": "{{ $('Webhook').item.json.body.full_address }}",
      "Service_Area": "{{ $('Webhook').item.json.body.customData['Service Area'] }}",
      "conversation-summary": "{{ $json.conversation_summary }}"
    }
  }
}

Make sure your integration actually passes this parameter to Twilio's API. If not, you may need to set it elsewhere in your call flow.
For more details, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

E

elderly-tomatoOP•10/13/25, 10:33 AM

when triggering it i get this error
400 - "{"message":["property machineDetection should not exist"],"error":"Bad Request","statusCode":400}"

@Vapi Support Bot

I am sending this request to vapi make a call API end point
i dont see an option to configure the request to twilio api

E

elderly-tomatoOP•10/13/25, 10:35 AM

I’m running outbound campaigns on the VoiceAIWrapper platform, and I’m noticing that Twilio’s Answering Machine Detection (AMD) is still being triggered — causing unnecessary charges and delays on live answer detection.

Since I can’t modify the Twilio call parameters directly via the Vapi create call endpoint, can you please disable AMD (Answering Machine Detection) on my account or for all outbound calls by setting machineDetection: none at your Twilio call initiation layer?

This will help avoid extra AMD costs and speed up call connects.
Thanks!

V

Vapi Support BotAPP•10/13/25, 10:36 AM

Vapi's "make a call" API does not support passing Twilio-specific parameters like
machineDetection
machineDetection
machineDetection
machineDetection in the payload, which is why you receive the error. To disable Twilio's Answering Machine Detection (AMD) when using Vapi, you must configure this at the Twilio account or phone number level, or contact Vapi support to request disabling AMD for your Twilio integration.
There is currently no supported way to set
machineDetection: 'none'
machineDetection: 'none'
machineDetection: 'none'
machineDetection: 'none' directly in the Vapi API call.
For further assistance, reach out to Vapi support with your use case and integration details.

Source:

Voicemail Detection | Vapi Documentation

E

elderly-tomatoOP•10/13/25, 10:41 AM

@Vapi Support Bot can you ggenerate me an email I can send to vapi support with the details of the problem and the wanted solution

V

Vapi Support BotAPP•10/13/25, 10:43 AM

Here’s an email template you can send to Vapi support:

---

Subject: Request to Disable Twilio Answering Machine Detection (AMD) for Outbound Calls

Hello Vapi Support Team,

I'm running outbound campaigns via the Vapi platform using Twilio as the carrier. Despite configuring Vapi as my voicemail detection provider, Twilio's Answering Machine Detection (AMD) is still active, resulting in duplicate voicemail detection charges and delays. Since I cannot set

machineDetection: 'none'

machineDetection: 'none'

machineDetection: 'none'

machineDetection: 'none' via the Vapi API, please disable AMD for all my outbound Twilio calls at your integration layer.

Thank you!
[Include your organization/account details here]

Source:

Voicemail Detection | Vapi Documentation

E

elderly-tomatoOP•10/13/25, 11:24 AM

@Vapi Support Bot

could that option be configured here
https://docs.vapi.ai/api-reference/assistants/update#request.body.voicemailDetection

on Assistant level in Vapi

Update Assistant | Vapi

V

Vapi Support BotAPP•10/13/25, 11:25 AM

No, the
voicemailDetection
voicemailDetection
voicemailDetection
voicemailDetection property in the Vapi Assistant configuration does not control Twilio's Answering Machine Detection (AMD). This setting only affects Vapi's own voicemail detection logic, not Twilio's carrier-level AMD. To disable Twilio's AMD and avoid duplicate charges, you must either configure it directly in your Twilio account/number settings or request that Vapi support disable AMD at the Twilio integration layer for your organization.

There is currently no supported way to disable Twilio AMD via the Vapi Assistant API or configuration.
For more details, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

E

elderly-tomatoOP•10/13/25, 7:29 PM

@Duckie can anyone help me with this

E

elderly-tomatoOP•10/13/25, 7:29 PM

support HELLO

V

Vapi Support BotAPP•10/13/25, 7:31 PM

The only way to resolve this is to contact Vapi support directly and request that Twilio's Answering Machine Detection (AMD) be disabled at the integration layer for your organization.
Reply to your previous support email (or open a new ticket) and reference your ongoing issue, including your organization details and a summary of the duplicate charges. This will ensure your request is prioritized and handled by the appropriate team.
There is currently no way to disable AMD via the Vapi API or Assistant configuration.
For reference, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

K

KyleAPP•10/15/25, 8:04 AM

If you want to disable VMD completely, use the dashboard UI, navigate to your assistant configuration and turn voicemail detection to

off

off

off

off . Just as a side note, Vapi VMD is Twilio and google combined.

E

elderly-tomatoOP•10/16/25, 5:51 PM

so Vapi uses Twilio thats why its enabled on my end??

E

elderly-tomatoOP•10/16/25, 5:51 PM

@Vapi Team @Vapi Moderator

E

elderly-tomatoOP•10/16/25, 5:51 PM

@Vapi Support Bot

V

Vapi Support BotAPP•10/16/25, 5:53 PM

Vapi can use Twilio as a carrier, but Twilio's Answering Machine Detection (AMD) is a separate feature that must be disabled at the Twilio account or integration level.
Turning off voicemail detection in the Vapi dashboard only disables Vapi's own detection, not Twilio's AMD.
To stop Twilio AMD charges, you must request Vapi support to disable AMD at the integration layer for your organization, as there is no API or dashboard setting for this.
For more details, see the Vapi voicemail detection documentation.

Source:

Voicemail Detection | Vapi Documentation

K

KyleAPP•10/20/25, 5:33 PM

Yes, so if you want to keep VMD but without twilio costs use Google VMD or turn VMD off on your assistant settings

Unexpected Twilio Charges for Voicemail Detection Despite Using Vapi

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