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Outbound Twilio calls fail using invalid, unassigned, and DNO numbers

Outgoing Twilio Programmable Voice and Elastic SIP Trunking calls will automatically fail if the From parameter (outgoing caller ID) contains one of these phone number types:

  • Invalid or unassigned phone numbers: This includes 7-digit local numbers that don’t belong to the dialed area code, numbers not currently in service, and numbers that have not been officially assigned an Operating Company Number (OCN) for carrier servicing.
  • Do-not-originate (DNO) number: A number that only accepts incoming calls.

Notice: Calls that are <Dial> forwarded via Twilio are also blocked under these conditions to protect you from incoming unlawful robocalls. <Dial> forwarded calls from ANONYMOUS are not blocked.

Check for errors

All outbound call requests with one of these phone number types will fail:

  • Outbound call requests submitted to Twilio’s REST API will immediately fail, with the response containing an error code in place of a Call SID. These calls aren’t tracked in Twilio’s call logs, so users will need to review their Twilio application’s logs or recreate the failure to view the flagged error code and associated details.
  • <Dial> forwarded calls will also automatically fail. These call failures are tracked in the Twilio call logs, and can be seen in Console, or via the REST API.

The following error codes are commonly caused by calls failed due to one of these phone number types:

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