With Skype for Business on-premises deployments, administrators frequently configure normalization rules to handle different dialing behaviors of users. This causes an invalid phone number to be passed to the PSTN when you use the Microsoft 365 Skype for Business Online PSTN International calling service.

These issues occur because the user is leaving the trunk code of 0 (zero) in the phone number sequence. Reason: Gateway responded with 404 Not Found (User Not Found) The following details are recorded in the UCCAPI logs from the Mediation server: Error message: SIP/2.0 404 Not Found For example, when a user makes a call to Australia by using the +61 02 XXXXXXXX phone number format, the call fails with the 'number not in service' error. Your call isn't completed successfully, and you may receive an error message.

When you dial an international phone number by using Cloud PBX with PSTN International Calling in Skype for Business Online (formerly Lync Online), you experience one of the following symptoms:

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