You are having trouble making or receiving calls and have noted that your Trunk or PBX is reporting abnormally formatted numbers

This issue is often the cause of a 403 error "No match for Service User Part" for incoming calls to Teams users.

Why Is This Happening?

Microsoft Teams and our SBCs expect all numbers to be in the full e164 format of +<country code><number minus leading zero>. This may not match your PBX or Trunk expectations.

So What Do I Do?

In the service portal, navigate to the Services tab and then either the PBX or Trunk tab accordingly.

Note the e164 format setting:

There are 3 options here:

  • e164 with +
  • e164 without +
  • Localized

The first 2 are pretty obvious but the third opens up further option boxes:

These 4 boxes strip off any leading + and country code, leaving the number without a leading zero. So now, using these fields, you can set the number to the format that matches your PBX or Trunk requirements.

10D dialling

For North American (US/Canada) customers Only.

If you dial a number without the leading 1 or +1, then E164 rules can be created to format this for Teams as below.

Similarly, if your service provider presents numbers without a leading +1 (or 1) then the E164 rules below will add the +1 to make this recognisable by the cenumber settings.


It may be worth trying some settings along with test calls to get this operating perfectly for your setup.