Account queries going on for months

I have been struggling with MTN for months now with no luck. In August / September last year MTN changed their system and since then every month my contract gets suspended. They say it's due to an outstanding amount of just over R1000 and I keep sending proof of payments made but still every month my phone gets disconnected again. I've spent hours on the phone trying to resolve this issue and to date have had no feedback from MTN. I ended up going into the store to try resolve the problem at which point the consultant informed me that I was due for an upgrade. I decided to do my upgrade but again I had to send the proof of payment before I could do my upgrade which I did again. We did the upgrade and suddenly I see I was charged R6851.93? I phoned MTN to find out what was going on and I was informed I was charged a migration fee because I changed packages. I told them I had to change packages because MTN doesn't have the package I normally take, the consultant agreed that this charge was incorrect and sent a query to their billing department - nothing came from this. So I phoned again and this time I was informed it was for an early upgrade fee? I told the consultant that the instore consultant told me I was due for the upgrade and that I have been with MTN for years and I've never been charged for an early upgrade, she also agreed this charge was incorrect and did yet another inquiry but informed me to go back to the store and get assistance from them too. I went to speak to the manager at the store he looked at my account and agreed that the charges were indeed incorrect and also sent an inquiry from his side. The next day I received a whatsapp message from him saying I did my upgrade 4 days before my upgrade date that is why I am being charged an early upgrade fee. I told him that MTN told me that I was due for an upgrade and that his staff should have told me about this ridiculous amount I would have been charged for doing the upgrade. Any person in their right mind would rather wait 4 days to do an upgrade if it meant that they would avoid a R6851.93 bill. The manager eventually decided not to respond to messages when I told him that his consultant should have informed me of this charge. Both my queries have to date not been resolved and my phone will be disconnected again soon because of MTN staff not knowing how to do their work. I have also requested my bills be emailed to me and I am still waiting for that too. Even when I receive a reference number when I phone them again they can't find any record of my reference and there is no notes made on the system... how do you do business like this? Who can honestly afford to pay almost R7000 in 1 month just to upgrade their phone? I really need some assistance in this matter please. The number in question is ***.