A gym I was part of required me to send my plastic barcode / keyfab to a PO Box in order to cancel my subscription. Kind of ridiculous. I'm pretty sure they'd continually charge me and send me to collections if the charges just got denied. Something to think about - canceling contractual subscriptions may require more than just a failed credit card.
There are two different things - contract cancellation and access to your account. They can be changed independently, and should be. Subscription contract usually does not transfer ownership, so you still own your account and should be able to deny its usage to anyone. It could be breach of contract but then they could use collections, courts, etc. to resolve it - that's different business.
