You have a number of users who do not have their own DDI number. For these, you would like to assign an extension number only.
You can use the extension numbers in the Teams User profiles in O365. Any number assigned to a user must be unique within the customer
You can manually input the extension number into the user settings (ignore the country setting at this stage):
A trunk user will need to have a number assigned. You cannot add a Trunk User without a number. If your trunk does not have a sufficient number of DDIs in the range(s) specified, you can add a dummy range of (4-digit or greater) extension numbers. These can then be assigned to users in place of DDI numbers.
Note that you may wish to consider how to distribute calls from DDI numbers to these users. This can be achieved by creating users as target groups in Teams where several users are group members.
Can I Use A Common Caller ID DDI For Several Teams Users?
In the Teams client you can withhold your own Caller ID:
You then have the following options
A PBX user may be able to use features in the PBX to present an alternative Caller ID (such as a group target number)
A Trunk user can present an alternative Caller ID via the From Header setting in the Trunk Settings page.
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