MTN incorrect Billing

I am writing a review for the 4th time now. MTN has been deducting a R1000 extra on my account. This is the 5th month now and this issue has not been sorted. I'm extremely disappointed for this appalling service from such a big company. I have just called 135 and I have to explain my query, all they do is keep escalating my query. I am now going to involve the law as I have ran out of options.