Members who have a "suspended" account should NOT have access to their data, benchmarks, etc. until they've settled their account at the previous box. The fact that you allow them to change boxes and take their data with them is not supportive of your clients. If they want to open a new account, fine, but don't give them access to the suspended account until they fulfill their obligation.
Thanks for the feedback. If an athlete is looking to join a new gym, we cannot stop them from having a new account created. If an athlete has their account transferred, we do always make them aware of having to contact their previous gym owner to deactivate their membership.