MTN - Extemely bad customer service!!!

I wish there was a minus 10 star rating because MTN deserves that rating in my experience! Have tried for a month to call to cancel a month to month contract but to no avail. Last month MTN supposedly cancelled the contract only to then be billed again. Tried calling numberous times only to be put on hold for a hour the first time around! Thereafter I ran out of patience and hung up after 30 minutes of holding! Demanded speaking to a Manager who said she would assist the next day by having someone call me but.... surprise, surprise, it's now a week and I'm still waiting for the call! I have been loyal to MTN for almost 20 years but no more I'm afraid! This experience has been the last straw!