A user/person with Global Admin rights in O365/M365 must be available to do the configuration.
A Microsoft license that includes Microsoft Teams. This license is only needed for a few minutes to activate a domain and can be cancelled or moved back to the original user when the task is done.
Microsoft Teams Phone Standard licence added to the users. E5 licenced users needs to have the Teams Phone feature enabled.
If setting up Auto Attendants and Call Queues, Microsoft Teams Resource Account licenses are required. These are free licenses and the need is one per AA and CQ. Order 20 licenses to have flexibility in the onboarding.