Worse service ever

Its been 5months since l have been fighting with MTN regarding my payments. I have sent them all my proof of payment which states that l paid them since May but clearly someone is not doing his or her own job to check where is this money. Last month l had to go to pay at Atm used the right reference which is my cellphone number still am getting statement that am owing. Am so disappointed with MTN l can't wait for my contract to be over and mover to another subscriber