Bad service from MTN to cancel a contract

My contract ended in October 2018. From then I have been on a month to month. Now when I want to cancel and go to Pay as you Go because MTN offers no good contracts I must pay a penalty for being on a stupid month to month. My 24 month contract is finished and you still you have to pay a penalty. I paid the penalty and sent proof of payment. No one is getting back to me after *****ing my money and even OVER charging me on my penalty no wants to give me answers. When I called I even get told my reference is wrong yet the reference is my cell phone number and the reference they reading is an automated reference by the bank. I have been a client with MTN contracts from 2000 and this is the treatment you get when you want to go to Pay as you GO. I was told email proof of payment and they will process it. After asking in my email for a reply no one rep****. After calling they say they cant do nothing. Yet I was asked for proof.