Disgusting service trying to cancel a contract

MTN has been so frustrating to deal with. I have been trying to cancel a contract with them since a few weeks ago. I have been calling their 135 number almost everyday. I have been told by numerous consultants that the Retentions department telephone lines are not working....how convenient. I was also told that I will be called back by someone in the Retentions department which never happened to date. Now they rebill me for another month and expect me to now pay a bill that was meant to be cancelled. I'm at the pits trying to deal with *********** service consultants who dont even try to help with a query. They just push you from one department to another or most days just put you on hold for what seems like forever. I have reference numbers for all the times that I've called. Please help...all I want is for my contract to be cancelled. I can't deal with MTN any longer. Their service is plain down pathetic. To top it off they send me this message via sms yesterday. Y'ello! Your 24-month MTN contract has ended. You're now on a month-to-month plan. Remember, you don't have any promo bundles and may be charged at out-of-bundle rates. Have a great day!