NOT TO CANCELL AN MTN CONTRACT

I have had a contract with MTN for more 10 years , decided to cancel even gave notice to cancel .My problem is my contract was not cancelled only to receive a statement saying i have a deduction this month. I even got my cancellation reference 1 - ***, never missed one debit order .I call and was told my cancellation was declined , i asked myself if i had a contract with the devil . All my debit orders go through i dont owe them. Why such kind of treatment to a once very loyal customer. Why try and tarnish my credit profile , if i had not made a follow up ,they would have continued debiting my FNB account .I gave adquate time for notice of cancellation. As a consumer i feel that my rights have been infringed.