Outbound calls. couldn't complete the call, check you are using the correct number format


Hi all,


I can't make outbound calls to PSTN, I get this error:


couldn't complete the call, check you are using the correct number format... check with admin blah blah blah


I get the similar error when I call that user number via PSTN from an Australian number.


  • I'm on an Australian tenant, user location Australia. User location was set to US so a US number could be assigned then set back to Australia. Have tried setting user back to US, made no difference.
  • E1 + Phone System + Domestic and International Calling Plan.
  • US phone assigned to the user, since we can only get Australian service numbers. Only using the number as users required to have a number to make PSTN calls.
  • I can call my Australian service numbers and the call flow works as expected and the user can take those calls.
  • I don't have any dialling plans setup. I didn't think I would need any.

Anyone got any ideas what the problem is?

1 Reply



By documentation an integration needs to be done first with Telstra PSTN service for you to make outbound\inbound PSTN call from Microsoft 365 (S4B\Teams):

 Not sure if this is completed prior to your testing, but I'd suggest to contact first Telstra for integration process as you've already provisioned services\user on your end.


Detailed Instruction:







Polite as usual,





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