Calls to an international phone number fail when you use Cloud PBX with PSTN International Calling

  • Article
  • Applies to:
    Skype for Business Online

Problem

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:

  • Your call isn't completed successfully, and you may receive an error message. 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.

  • The following details are recorded in the UCCAPI logs from the Mediation server:

    Error message: SIP/2.0 404 Not Found
Reason: Gateway responded with 404 Not Found (User Not Found)

Solution

These issues occur because the user is leaving the trunk code of 0 (zero) in the phone number sequence. 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.

With Skype for Business on-premises deployments, administrators frequently configure normalization rules to handle different dialing behaviors of users. However, when you use the Cloud, international phone numbers must be dialed in the format of + (Country Code)(Area Code)(Local Number). In the earlier example, the phone number should be dialed using the following format: +61 2 XXXXXXXX.

More Information

Depending on the particular PSTN calling infrastructure and telephone carrier, users are accustomed to dialing numbers that include the 0 (zero). Administrators remove this number in the dialing sequence elsewhere in the telephone infrastructure before it's passed to the carrier. Currently, there's no way to strip or normalize the phone number before it's passed to the PSTN when you use the PSTN international calling feature in Skype for Business Online.

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