Additional Data charges

I recently opened a month to month contract with Mweb for the 5Gb per month deal and its only been two days and I realised that they are charging more than my actual usage. After being put on hold for over 10minutes being number 1 in line for another 5mins and an arrogant technician saying I am wrong. All I want is to pay for this month and discontinue the use really not interested in their stupid explanations that don't make sense. I switch off all updates on Applications and only check my mail and facebook not to mention the network is extremely slow in the evening and could not study late at night because of constant disconnection. I moved to Mweb as I believed it would be a saving and I am glad I picked this up before they charged me for additional usage that doesn't exist. From the 26th to the 28th January my usage is 381Mb but on their website they have 740MB for 2 days, which is utter *******. I have been using 2Gb per month on my mobile data how do I accumulate 700Mb in two days without updates or video downloads and watching videos online. had I been warned that they rip people off would have never even entertained their calls. They should call so I can cancel.