If a customer has created their own account rather than claiming the one that you created for them, then you can easily resolve this by archiving the admin created account.
You can identify which profile needs to be archived by clicking in to the customer record via the Customers page. The account that you created will be marked as Unclaimed at the top of the details page whereas the record linked to the account your customer created themselves will have no markings referring to claimed/unclaimed.
Click the Archive button in the top right hand corner of the customer's unclaimed record. Don't worry if you do happen to archive the wrong one, it won't affect the customer's account and you can quickly and easily unarchive the record if needed by going to Customers > filter this page to Archived > click on customer record > Unarchive.
If you need to transfer any pre-existing credits or sessions over to this customer created account then you can easily do this by gifting them the relevant package and adding the customer onto sessions from within their customer record. Please note that this customer must be following your business in order for you to be able to action this. You can find more information on how to do this within our How do I add and onboard / migrate my customers? article. We would also suggest removing this package and sessions from this now archived unclaimed account.