https://docs.microsoft.com/en-us/microsoft-365/admin/misc/become-the-admin?view=o365-worldwide

Had to go through this process for a customer, because their VLSC account was setup at some stage in the past using licensing@ VLSC account as a work or school account, the domain  was already registered against an unmanaged Azure AD directory, so we couldn’t set them up to use Teams. It’s a straight forward process just follow the article.

To find out if a domain is part of an unmanaged Azure AD directory, you can follow https://docs.microsoft.com/en-us/power-platform/admin/powerapps-gdpr-dsr-guide-systemlogs#determining-tenant-type as specified in the article.