Internet Services Pathetic

I have been using MTN services for such a long time and have never had any issues till beginning of this year. I would by 100 megabytes of data and within a few minutes it would all be gone. Phoned to find out what could be the problem, I was told that its internet usage. I then deactivated everything including whatsapp and it got even worse. phoning MTN was a waste of my time because nobody could explain what was wrong. The reason l got was its my internet that is consuming my data. on one day l recharged with close to R 500 because l needed to use the internet, and this didn't even last me the whole day. I mean come on, how much of internet can l use for that much. the technicians at MTN could only tell me that l need to log an enquiry so they can send me the sites that are consuming the data. I have since stopped purchasing airtime, data buddles, but what's the point of then having a phone if l cant use it? Just yesterday (14/04/16) I received my monthly data of 300 mb, today is the 15th and its finished. what the hell? Just earlier this month, MTN called to say l am due for an upgrade, really? For what?