To whom you can assign Teams subscriber and service phone numbers ?

 Copilot

In Microsoft Teams, phone numbers can be assigned to different entities based on their type:

Subscriber (User) Phone Numbers:

These are assigned to individual users in your organization. Each user can have a unique phone number for making and receiving calls1.

Service Phone Numbers:

These are assigned to services such as Audio Conferencing, Auto Attendants, or Call Queues. Service numbers have a higher concurrent call capacity compared to user numbers

Audio Conferencing bridges

When you set up Audio Conferencing for Teams meetings, you get an Audio Conferencing bridge. The bridge answers the call for users who are dialing in to the meeting using a phone. The bridge answers the caller with voice prompts from an Auto attendant, and then, depending on your settings, can play notifications, ask callers to record their name, and so on.

A conferencing bridge can contain one or more service phone numbers. A service phone number is a number assigned to a service, such as Audio Conferencing, rather than to an individual user. The phone number you set is included on the meeting invites for Teams.