Applies To

Call2Teams - Customers


The default setting for differentiating between an external PSTN call and an internal extension is based on the following logic:

  • If the dialled number is 6 digits or shorter, it is considered an extension number
  • If the dialled number is longer than 6 digits, it is considered an external PSTN call

In some unusual cases customers may wish to amend this to allow for extension numbers of greater length than 6 digits.


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

In summary, duplicate the Call2Teams normalization rule within the Global dial plan, and then modify the duplicate to match longer numbers.

Begin by logging in to the customer's Microsoft 365 Admin Portal.

Select Teams Admin Center, then on the Left Navigation go to Voice: 





  • Click Dial Plan
  • Click  Global. Click this should now show 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 automatically  converting these to E.164.

  • 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 regular expression (regex).
  • The 'If' condition by default is: ^([\*\#][\*\#\d]+|[1-9]\d{0,5})$
    • If users are unfamiliar with regular expressions the important number is the near the end of the string above. Increase this to 6 in order 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 the new rule is above the existing normalization rule on the global dial plan, as in the screenshot below: The 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 unchanged, as this will be checked by Call2Teams sync and amended if different from the expected default.


If customers 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 Microsoft 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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