Cell C unwilling to assist re: my invoice!

There is a query I have about my statement and their twitter social media consultants could not be bothered to assist me! they keep saying "we billed you correctly" without even trying to understand what my problem is. I ask for a call back and no one calls and they keep referring to the call that I missed a week ago, I have requesting for a call back instead get answers like "refer to your invoice". How rude?! I WANT MY CONTRACT CANCELLED! YM^ certainly lacks comprehension!