MTN SA - BEING CHARGED TOO MUCH ON MONTHLY BILL - NO EXPLANATIONS

I am absolutely horrified with the service I am receiving from MTN. I have two contracts with you guys amounting to R600. My bill for October - November was not debited in November - the agents could not give me a reason for this. I also did an upgrade on November 20th and my new amounts for both contracts would be R679. The upgrade was done by a retentions agent and I was assured that all would be fine. I received my invoice today and the outstanding amount to be debited is R2974.99. This is absolutely unacceptable. According to me, my bill should be around R1200 / R1300. Is this what you do to all your customers? Charge them and then not be able to explain why...I have tried to get help from the call centre but it seems that no one knows exactly what is going on. I expect somebody to sort this out before the debit order goes off this month. Contact me on ***.