CANNOT CLOSE ACCOUNT AFTER FULL BALANCE IS PAID

My Wife has a Makro Credit Card - biggest load of ****.. we went in Saturday morning to Makro to the Cashier and asked for a settlement as we would like to pay the account and close it, we get given a print out of the settlement and my wife called the Friday for it too, we paid just on R6000 to settle the account and then we proceed to customer care as we were told we must call to close the account, the person on the line tells my wife she cannot close the account as there is a balance due of R70 odd rand, how the hell is that possible when we just paid the account in full.. something about Interest, bull ****, interest on an account in a zero balance? I want this account closed today or I will contact the Consumer Council and at the same time I will ask Carte Blanche to investigate RCS as they RIP their customers off completely, Sort this out today, we will not pay you another cent.