Bad Service from Accounts Department

I paid up my Game account and then received a statement a month later for "Interest" and a "Monthly Fee" that must be paid. The payment was collected via debit order. A few days later I visited the Welkom Game store and asked that my account must be closed. They simply just told me I must come back at another time. I was there at the time, why can't they assist me with closing the account. Now I must travel back and forth for what? And why must a Monthly Fee be paid, when the account is empty? This is not right.