Over charge for Data Usage

I made my first inquiry on the 12 November 2015 about my data usage being ridiculously high for the last few months. Customer care said it would take about 24 to 48 hours to get back to me and it's been a month already without a resolve. My upgraded contract started on the 1st December and already on the 7th 3 GB's of data has been used up already? It just doesn't make sense! I requested the warning SMS to be sent to me when my data is low and that hasn't happened either. I am feeling rather desperate now that I am being charged over R2500 every month for my contract where I shouldn't be - how do I escalate this problem and get it sorted? No one seems to be assisting - do I need to get lawyers involved?