Closed account but still been charged admin fees

I paid off my RCS account in March. I went into store to close the account and was told to phone the call center. I called the call center and was told a note has been made. A few months later I get a call from RCS saying I have an outstanding amount. This was admin fees as the account was not closed. I made the payment and yet again requested the account to be closed. This goes on every month. Today I get a call again and this time when I refused to pay as I have requested no less than 20 times for this account to be closed. I was told I have to go in store to close this account. I officially give up. RBS is useless.