You can either change or block the Caller ID (also called a Calling Line ID) for a user. By default, the Teams or Skype for Business Online user’s phone number can be seen when that user makes a call to a PSTN phone, or when a call comes in. You can create a Caller ID policy to provide an alternate displayed number, or to block any number from being displayed. Note: Identity must be unique. ServiceNumber must be a valid Service Number in the Skype for Business Online online telephone number inventory. If CallerIdSubstitute is given as “Service”, then ServiceNumber cannot be empty. If CallerIdSubstitute is given as “Resource”, then ResourceAccount cannot be empty. Preview The use of the parameters ResourceAccount and CompanyName is in Preview.
— Read on docs.microsoft.com/en-us/powershell/module/skype/new-cscallinglineidentity