This is an important change to be aware of. Previously, a Teams Phone Resource Account license (previously called Virtual user license) was only required when assigning a phone number to a resource account.
Now, all resource accounts used in Microsoft Teams must be assigned a Teams Phone Resource Account license, regardless of whether they’ll be assigned a phone number.
All auto attendants and call queues in Microsoft Teams require an associated resource account.
Will I have enough Teams Phone Resource Accounts?
Organisations may be concerned, as resource accounts are required for auto attendants and call queues, and this may now limit the number of auto attendants and call queues they can create and use.
Each tenant is allotted Teams Phone Resource Account licenses based on the number of user licenses of Teams Phone Standard (included in E5) or Teams Phone with Calling Plan (a single combined SKU).
Any organization with a minimum single subscription with Teams Phone features is allocated 25 Teams Phone Resource Account licenses at no cost.
One more Teams Phone Resource Account license becomes available for every 10 user licenses with Teams Phone in your organization.
Microsoft suggests this ratio will cover most organisations’ requirements.
Also, you can’t assign a Teams Phone Standard license (or excess E5 user accounts) to a resource account. You must switch to a Teams Phone Resource Account license if you currently have resource accounts configured with Teams Phone Standard licenses.
Will I have to pay if I need more Teams Phone Resource Accounts?
These licences have always been 0 cost and I don’t believe Microsoft intends to monetize these.
You can go into the portal and order more at no cost; I was able to add 50 to my tenant at zero cost.
I imagine Microsoft is giving themselves the option to limit these if the ratio of Teams Phone licenced users to auto attendants and call queues is way off.
Reference: Microsoft Teams Phone Resource Account licenses on learn