If you need to pass over ownership on the account to another user, you can do so with a few clicks.
The new owner will need to be a user in the account. If you need to create them as a user, please follow the step here: Add a user to your Groove account
Change the owner of your Groove Account
The current account owner can change ownership by going into Settings > Company > Billing > Manage Account in the left sidebar.
Under Manage Account, you'll see a dropdown menu next to Account Owner. Select the user you'd like to transfer ownership to and press Update.
Once the account owner has been switched, the new owner will have full access to the account, including the Billing section. The former owner will now have admin right and access to billing is denied.