Ripping me off

I have a loan with african bank, i fell behind. I made arrangements for them to deduct extra off with they did. Then they deducted an extra R100, And when i went to query, tgey said i was suppose to call to stop it. They must know they must stop it coz it was just for the overdue amount. Tgen i was told to email copy of bank statement. I did that. Didnt get my money back. They just kept replying to email it again. Tgen i called head office. They told me how much is my outstanding balance. Im suppose to finish them at the end of august, witch is R868.70. now i get a statement not even a week later, and now it sais i owe R986.09how on earth can that be correct. This is a total *******. They alreddy took more extra payment than they were supposr to, and now every day when i see the installment is more. I am disgraced by this and the staff are rude to the clients. I want to know WHY DO THEY ADD MORE MONEY EVERYTIME????