African bank credit card

African bank are ****mers, I've been paying for a credit card that I'm not even using, but the surprising thing that amount doesn't go down, they keep calling me saying my account is in arrears while I'm paying every month, sometimes they deduct less money and put my account on arrears and the next month I have to pay double, I tried closing the my world account but african bank doesn't want to close that my world account.