Well this is good news! Previously there was a requirement to assign a Phone System licence to all Call Queues and Auto Attendants that had a phone number assigned. Now with the new “Phone System – Virtual User” licence, you can do this at no cost.
“New application instances will require the creation of a Resource Account, licensing it, and associating it with your application instance. Only resource accounts with a phone number need to be licensed. Update: a $0 application license (Phone System – Virtual User) can be acquired and assigned to these resource accounts. NOTE: please note that the know issue listed below (Removing phone system license corrupts the resource accounts) is still not resolved. To avoid interruption to your application, create a new resource account and license it with a virtual user license, associate it with the application and then switch the phone number to it.”
For more information see the announcement here. To learn how to purchase this free licence and assign it, see Add a free licence to Call Queues and Auto Attendants (Microsoft Teams).