Applies To

Call2Teams - Customers


The default setting for differentiating between an external PSTN call and an internal extension is based on the dialled number being 6 digits or less for an extension or greater for an external PSTN call. In some unusual cases you may require to amend this to allow for extensions of greater length.


There is a workaround for this which can be achieved via the Microsoft Team Admin Center.

The summary is to duplicate the Call2Teams normalization rule within the Global dial paln and then modify the duplicate to match longer numbers.

Start by logging in to your Office 365 Admin Portal and Select Teams Admin Center, then on the Left Navigation go to Voice 








  • Dial Plan > Click Global. You should now see the normalization rules. Call2Teams creates a rule that allows feature codes (dialed numbers that start with an * or #) and short numbers to be passed through as-is to the far end. Short numbers are considered extension numbers and so we match them with a rule to avoid Teams converting these to E164.
  • Click Add by the normalization rules table. Enter a suitable name and description, perhaps mentioning that the purpose is to match larger extension numbers.

  • Selected 'Advanced' to allow use of a regex.
    • The 'If' condition by default is: ^([\*\#][\*\#\d]+|[1-9]\d{0,5})$
    • If you are unfamiliar with regular expressions the important number is the 5 near the end. Increase this to 6 if you want to match 7 digit extensions (note we assume extensions start with an explicit 1-9, which is why this is one less than the total number length). For example: ^([\*\#][\*\#\d]+|[1-9]\d{0,6})$
    • The 'to' condition should be $1
  • The existing normalization rule should be left untouched. Ensure your new rule is above it on the global dial plan, .e.g below you can see new Normalization rule is created as “My Company rule” and the dial plan is set for the Teams users to dial number maximum of 7 digits




Note: It's important that the original rule is left untouched, as this will be checked by Call2Teams sync and amended if different from the expected default.


If you make use of an external line access code, this feature will not work at this time since the portal is not affected by amendments to the MS dialling rules and will continue to treat digit streams of 7 or more digits as external PSTN numbers and prefix these with the access code.

Further Reading

Dialling Rules

Microsoft Dialling Plans & Normalization Rules


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