Licensed users can call out to numbers located in the country/region where their Microsoft 365 or Office 365 license is assigned to the user based on the user's location, and to international numbers in 196 countries/regions.
All users in the same country/region (this is the user country location defined in the licensing area of the Microsoft 365 admin center) with the same Calling Plan share a pool of minutes. For example, if you have 100 users located in the same country/region with a 120 minutes Domestic Calling Plan assigned, they share a pool of 12,000 minutes. All calls exceeding these minutes are billed per minute.