Cancellation of membership

Exs gym contract is in her name but the banking details is in mine. She asked the gym to cancel it but they moved it over to retention or whatever. Why don't I have a say because it is my BANK ACCOUNT not hers. This is utterly pathetic of virgin active to treat a client like this. I have a membership but I'm not willing to pay for hers anymore and it is past the contract period so they must close her account if I don't want to pay for it.