I am being ****** of data by MTN

I am on a package wherein I get 2GB data every month, as well as 2GB night express data. I get this data on the 21st of every month and use it on my laptop. I only access the internet moderately but the data gets depleted like you will never believe. I visit a facebook page for five minutes and then 700MB is gone. This is unacceptable. MTN *****s and robs consumers on a daily basis. To top it all, just this month, I noticed that my night express data is short of 800MB, but I have not even once accessed the internet between 00h00 and 5:59am, NOT EVEN ONCE! How does my night data disappear when I never ever use it at all? I called 808 got no assistance, THEY CANT HELP! I called 1555 and they told me about possible background updates, but I know its not because I have set the laptop TO NOT update automatically. I have a Vodacom SIM I use on the same laptop and 200MB lasts me a lifetime. There is nothing wrong with my laptop settings, its MTN robbing clients. I pay R329 every month without fail for this useless package but my data disappears in days. MTN what is going on with you? My contract expires in 2017 only, will I be subject to this ABUSE until then? I regret ever knowing you.