Bad service

I took out a contract phone for 24 months 2015 a Sony Experia E4G account number A ********** cellphone number ********** 460 @ carnival mall. The Contract expired in September 2017 I never got a chance to cancel the contract due to health reasons. December I called to cancel the contract which was cancelled not knowing the someone already upgraded my contract in October. I then got a call from MBD advising that MTN has handed me over to them for my contract and I must pay R17000, I advised the lady that I will call MTN to find out as I believe my contract with them is finished and didn't understand why I'm owing them so much money. I called MTN in April 2018 and was told that I upgraded my contract in Ladysmith which I never did. I was then advised to send through an affidavit and a certified ID copy through to them and they will escalate to their legal department to investigate. I called after a month and was told that my query was never submitted to legal and I should re send the documents again. I did that on the 15th of May 2018 and the lady emailed me back with the reference ( 1- ********** 1486) to say that my query had been escalated and it should take approximately a month or so for them to get back to me. Now in August I called them to find out what's the progress of my query and was told that they have not yet started investigating my query and now they tell me the contract was done telephonically and not in Ladysmith. How long does it take to investigate while I am being harrased by MBD everyday with calls and smses demanding that I pay that money of which I know nothing about and my fear now is that I'll be blacklisted for something that I do not know. And yet no one seems to know anything of why the matter is still pending and why no one has not yet contacted me regarding this query . I would really appreciate urgency in this matter as this reflects on ITC that I owe MTN.