MTN False accusations

I have had an MTN account from the time of MTN inception. Due to the problems i had with billing i ported out one number and cancelled(i assumed) another. I was handed over for non payment of one account, i was given the option to pay up and continue or pay up and terminate(a little extra than the first opion). I chose to terminate, subsequently i terminated both accounts. When i call MTN/go to MTN store i am told my accounts are closed, however i cannot get a closed up letter. I then went to 14th avenue to be told that BOTH accounts have monies owing(to my knowledge and confirmation by MTN stores i had paid up both). I was not billed in the period alleged that i owed money, i was provided a letter that says i have paid up and should be closed(the handed over account). however at 14th avenue i was told i owed money and i need to pay on both accounts, no amount of trying to explain that i paid up and i closed this account made a difference, nor the fact that i have a paid up letter. I paid the outstanding amounts on the accounts, finally received a letter confirming i have no accounts and i owe MTN no amount of money. A year later i am being harassed by a collection agency(rude arrogant people that have no ethic being a legal company MBD!) I called MTN and i was told my account has been handed over. I went to 14th avenue and they in fact confirm that i owe MTN an amount of money and they have handed me over, despite me having a paid up letter from the 14th avenue legal department. I have never been billed for as well in the year. Over some time i am told my number has been recylced and the outstanding amount is not mine, it is for the new owner. The MTN legal department will contact the collection agency and sort it out. I was not given any confirmation etc as i am told i received a closed up letter last year. I cannot get hold of anyone at MTN legal to correct and update the collection agency, i have sent the collection agency proof of my payment and they still harass me endlessly. I cannot get this sorted out. MTN is recycling numbers, but the non payment and credit defaults are going against my name and ID number. No amount of tries is getting this sorted