Wrongfully billed and still no response

I have tried to call MTN on their help line a number of times with being placed on hold for an hour at a time and at the end hanging up as life goes on while you are on hold.I went to upgrade my phone in April 2015 and was currently on a top up plan for R209 per moth to a new top up plan of R299 per month. End of May, June and July I got credited on my bank account with amounts that did not come close to R299 per month and was much lager amounts. End of July I went to a MTN store and got a ref number but end of Jul the same thing happened. I then went to another store and got another ref number. I also stopped the debit orders and also reversed the last payment. this is now 18days later and surprise surprise I get an sms that says they will suspend my account if I do not pay the outstanding amount. How do you sign up for a top up then get money taken out of your account and you take time to sort it out and 2 months later things are still far from sorted out