*********** staff/ bad service

I requested MTN SA to cancel my contract as I was not renewing it after 24 months. I have reference numbers, I have contacted the customer care numerous times without joy, I have been to the branch and it is still not cancelled. at some stage a consultant from retention called trying to sell the product to me , I advised her to cancel the contract and she confirmed that it has been cancelled. I received SMS confirming cancellation. MTN is still billing me. MTN keeps threatening me with legal action and the issue is with them. If they hire *********** employees by not actioning customer request, why should I be held liable or having unreliable systems that do not action commands.