CHARGING MORE THAN THEY SHOULD

I HAVE TWO CELL CONTRACTS AT MTN. WHEN I UPGRADED I TOLD THEM A THOUSAND TIMES MAKE SURE IT IS A TOP UP ACCOUNT SO THAT WE CANT GO OVER THE LIMIT. NOW I FIND OUT THAT THEY NEVER DID AS THEY WERE TOLD AND THAT IT IS AN OPEN ACCOUNT. THATS WHY MY CELLPHONE ACCOUNT IS SKY HIGH. AND THEY CHARGE ME MORE FOR SERVICES FEES ON BOTH ACCOUNTS THAT WHAT WE UPGRADED TO. I WANT THIS SORTER OUT ASAP. MTN IS COSTING ME MONEY FOR THEIR MISTAKES. SOMEONE BETTER CALL ME AND SORT THIS OUT.