Cell C is useless

My experience with Cell C has been a terrible one, after settling my account with them over a year ago. They came back stating that I owe them R70 over a month ago I paid the R70 at the atm. However, they are refusing/unable to provide me with a paid up letter. I made the payment at the ATM as I was advised by one of their consultants at the cell c store in cresta. It is unfortunate that the atm I used was unable to print receipts. A month later still no update or anything, I have called received reference numbers been to multiple stores but No one is able to help. They all keep telling me that my number is not a contract anymore and all I want is my paid up lettwr