I’m trying to use a toll-free number (connected from Twilio through a SIP trunk)

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Hi Retell AI Support Team, I’m trying to use a toll-free number (connected from Twilio through a SIP trunk) for outbound calls in Retell AI. However, it seems that Retell AI is not accepting the toll-free number — while my other numbers are working fine. Can you please confirm if toll-free numbers are supported for outbound calling on Retell AI? If they are, kindly advise what steps or verification are required to enable this. Thank you for your support. Best regards,

I'm trying to import a VoIP.ms number via SIP trunking
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Based on the available documentation, toll-free numbers are supported in Retell AI(1). You can purchase toll-free numbers directly from Retell for $5/month(1), and toll-free numbers cost $0.06 per minute for inbound calls(2).

For your specific situation with a Twilio toll-free number connected via SIP trunk, here are the key steps to verify your setup:

1. Verify Your Elastic SIP Trunk Configuration(3)

Ensure you’ve completed these steps in Twilio:

  • Created the elastic SIP trunk with proper termination settings (for outbound)(3)
  • Set up the termination SIP URI correctly(3)
  • Configured authentication either via IP whitelisting or username/password credentials(3)
  • Set up origination (for inbound) with Retell’s SIP server address: sip:sip.retellai.com(3)

2. Import the Number to Retell(3)

After moving your toll-free number to the elastic SIP trunk in Twilio, you need to import it to Retell(3). Supply the termination SIP URI you set up in Twilio(3). If you configured auth via credentials, provide the username and password as well(3).

You can import the number either through the dashboard or programmatically via the Import Number API(3).

3. Common Issues to Check(3)

If outbound isn’t working:

  • Check your Termination SIP URI for any spaces and remove them(3)
  • Use a localized termination URI near your region(3)
  • Verify your username and credentials are correct (the username is different from the friendly name)(3)

4. International Dialing Setup(3)

If you need to set up dialing to international countries, search “geo” to find the “Voice Geographic Permissions” setting(3).

Once properly imported, your toll-free number should work for both inbound and outbound calls just like any Retell-purchased number(3).

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