Currently it is not possible to transfer the account ownership to another user for any reason, you can share your project with other users (with limited permissions).
We are evaluating adding the ability to transfer accounts in the future but at this time we do not have an ETA for this feature. If you require an alternative it is possible to create a new Strapi Cloud project and use our DTS feature to transfer your database and assets over to that new project and then cancel your existing project.
Note that all of our billing is done on the first of each month so if you wish to avoid additional charges you should do this towards the end of a month.
If you have any questions you can contact our support team via the help icon in the lower right on the Strapi Cloud dashboard.
Support Portal