Over billed....!

Not impressed with Mtn at all.... My account this month has been billed incredibly wrong... My bill every month should be R325 for the month of November I was charged R1087, 75. I have a capped prepaid contract so this shouldn't even been possible... Every time I try and phone to query this I get put on hold or sent to the wrong department... This is INCREDIBLY FRUSTRATING as the only way to solve this is to phone... I have found out that I have been charged for sending 832 mms... Who sends mms anymore.. This charge MUST get reversed it is ridiculous... I don't have money like this to waste....