Overcharge on contract

I have a R99 internet contract with Neotel , this entitles me to 10 G of data per month, for the last three months i have been receiving statements of values ranging from R700 - R1200. This is not the first time , when i last enquired, my billing, the amount dropped to about R200-R400.<br> <br> I have not yet called there service centre as the last time i requested a report of the device drawing the data they said i cannot get it.<br> <br> could someone send me an itemised billing as well as report on teh device drawing data, <br> <br>