The owner of the billing account is the user who owns the main email used to register the account.
By default, this user has full rights to manage the account. You cannot delete this user (since all information about orders, payments for services, as well as correspondence with technical support specialists on all issues is associated with him).
But the account owner can add one or more users and provide them access rights at his discretion (full or partial).
More details can be found in the Knowledge Base article:
Also, the owner of the current account can transfer any of the services of his account to another user's account.
For information on how to do this, see the Knowledge Base article: