Suspended cell phone MTN

I WENT TO MTN IN SPRINGS MALL TO CHANGE THE PACKAGE FROM AIRTIME TO DATA BUNDLE EVERYMONTH THEN I WAS TOLD THAT SINCE I WAS PAYING R250 I'M NOW GOING TO PAY R204 EVERY MONTH WTH NO EXTRA COST .SUDDENTLY DEBIT OF R950 WENT THROUGH ON MY ACOUNT .I REVERSEDIT SINCE IT WAS TOO MUCH FOR ME AND PAID NORMAL R205 SECOND MONTH SAME THING HAPPED I WENT TO THEM 5 TIMES ALREADY THEY PROMISE TO SORT THIS MATTER NOW MY PHONE IS BEEN SUSPENDED WITH NO REASON AT ALL PLEASE HELP