Worst Service Provider Ever_Cancelled contract handed over

MTN is the worst service provider ever, and everyone I know who has dealt with them agrees. My Story: I took out a contract with MTN in November 2013 for an iPhone. I was advised my one of their consultants to take out insurance, so I did. In Dec 2015, the phones fell and as a results the screen cracked. I sent through a claim which was not responded to until I wrote I review on hello peter. Long story short, I ended up cancelling the insurance and fixing the phone myself. In August 2015 the phone got lost, I reported this but the number was not cancelled and I did not do a sim-swap. They continued to bill me for airtime and data. November 2015 was suppose to be the end of my contract but they continued to bill me at R195 per month. I was confused as to what the amount was for so I stopped paying. On April the 24th, I called to have the contract cancelled but I was told I cant cancel since there is an amount outstanding. On April the 25th, I paid the whole amount outstanding. On the 26th of April I called them and was told by the person on the other side that she confirms the payment has been received and will send in a cancellation request. On May the 6th MTN handed over my account to debt collectors. What? On the 12th I receive an email from them telling me in a very unpleasant tone to settle my MTN account, I respond by saying the account was settled with MTN two weeks ago. I then sent through a query to MTN about the matter. I get a response your account has been Migrated to prepaid. Today I get another mail from the collectors asking for proof of payment. what on the earth should I do now. I do not appreciate such mails or calls especially when I've paid you an amount for data and airtime I never used. Advise to everyone. Stay away from MTN.