Mtn does not care about customers

I had a contract with mtn which i payed 1200 monthly. I then decided to do early termination of contract. I called them not sure about the date but thy told me how much am owing them. On the 14 of April i payed 17220 To them til today thy claiming thy can't see my payment to make matters worse they deducted again the monthly fee for this month. It ws only yesterday that the consultant that helped me told me that they gave me a wrong reference now whose fault is it?? Please help me because this is alot of money Thank you