Absolutely and utterly useless!

I upgraded my contract in August. Since then I have only been billed the correct balance once. At first I had been undercharged, so I called MTN and queried it and it had turned out that a mistake had been made in the accounts department. I was then charged that same amount for the next two months. I'm not sure why, as I had called and the issue had supposedly been sorted out. I was then charged the correct amount the following month. Then I started being charged more than what I had signed up for. I thought that it was just a credit due amount so I left it for the first month. When I was billed extra for the second month I called in again. I was told that it was because I was put onto an MTN Choice with no limit on my account. I can't understand how that happened as I was simply upgrading from my MTN Top Up Contract. The man said that he would put a limit on my account and I wont be billed anything extra from then on. This morning my bill came off, and of course I have been billed extra yet again. I have now tried calling 808 three times only to have the call end on me each time. If this issue isn't handled by 7 April 2015 I will place a stop payment on this account.