Do you mean adding dial-in numbers for meetings in Teams?
If you're scheduling meetings from within Teams, make sure PSTN meetings are enabled for your account. For more information about PSTN connectivity options, please refer to: https://learn.microsoft.com/en-us/microsoftteams/pstn-connectivity
If the dial-in number isn't available for conferencing, the correct license might not have been purchased or applied. Regarding the purchase of licenses, we recommend that you consider posting in the Microsoft Community or contacting an expert for better support.
In addition, you must send the meeting invitation to at least one person for dial-in information and join links to appear.
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