ARREARS!!

MY ACCOUNT WAS IN ARREARS WITH R930 NO ONE PHONED ME AND I DID NOT SEE THAT THE DEBIT ORDER DID NOT GO OFF AND ONLY HALF OF THE DEBIT WENT OF AFTER NO CALLS FROM THE BANK TO NOTIFY ME OF THE ARREARS THE LOAN WAS PAID OFF AND THE CONTRACT WAS EXPIRED, WHEN I WENT THROUGH MY STATEMENTS I SAW THAT I OWE THEM R930 RAND THAT I HAVE PAID IMMEDIATELY, THEY NOW SEND ME A STATEMENT WHERE THEY ADDED 29.50 % INTEREST ON ALL THE DAYS THAT THAT AMOUNT WAS IN ARREARS I WILL NOT PAY THAT INTEREST FROM R930 RAND THAT IS PAID THEY NOW WANT AN EXTRA AMOUNT OF R7186.30 WHICH IS CRAZY I WILL NOT PAY THIS INTEREST ON THIS ACCOUNT AS ALL THE MONEY I OWED THEM WAS PAID UP. THE INTEREST IS NOT MY PROBLEM AS THE STAFF DID NOT DO THEIR JOBS.MY ACCOUNT IS PAID UP TO DATE AND I WILL NOT PAY THAT CRAZY SUM OF INTEREST.