OVER CHARGED FINANCE CHARGES

I GOT UNDER DEBT REVIEW IN 2017 WITH NDC AND IT LOOKS LIKE THE DEBT WAS NEVER RESTRUCTURED, BALANCE OWING ON ACCOUNT AS AT AUGUST 2017 WAS R8240.42 AND PAYMENTS ARE CONSISTENTLY MADE HOWEVER BALANCE NEVER DECREASED. THE MONTHLY FIN CHARGES ARE NORMALLY R106.81 SINCE 2017 TO DATE, THEN LAST MONTH I INCREASED MONTHLY INSTALLMENT TO R220 AS PER THE MINIMUM PAYMENT REQUIRED ON MY JET ACCOUNT. I THEN REALIZED THEY INCREASED THE FINANCE CHARGES TO R109.85 EVEN THOUGH BALANCE WENT DOWN. PLEASE ADVISE AS TO HOW INTEREST IS CHARGED AND WHATS MAKING IT INCREASE EVEN THOUGHT BALANCE GOEWS DOWN. THE OUTSTADING BALANCE AT BEGINNING OF OCTOBER WAS R8,791.06 THEN PAID R332.35 WHICH NOW MAKES BALANCE TO BE R8,458.71 AFTER PAYMENTS WERE MADE. WHAT IS MAKING INTEREST TO GO UP. I CONTACTED CONSUMER FRIEND WHICH IS THE VENDOR HANDLING EDCON ACCOUNTS AND THE CONSULTANT COULDNT GIVE PROPER EXPLANATION.