BAD SERVICE MTN CONTACT CENTER

Very bad service received from MTN. I called to cancel my contract which was ending 31 March & till today cancelation was never done.Now they have send me a bill whereas I have cancelled my contract .I have made several follow up and no bother bothered to give me feedback on what is the way forward. I have been in contact via email with one of their agent & she advised she escalated the matter to her supervisor & still no one is giving me feedback.When you called them 1 is advised calls are recorded but to my surprise they can't get my call with the AGENT the time I called in to CANCEL