2GB Data depleted in a record 30min!

I purchased airtime (R110) and Data (2GB @ R249) on the 13/05/2016 for my Sony Z3. I used my phone as a hotspot to surf on the internet via desktop and with normal everyday internet surfing, 2GB was depleted within 30min. How so, when I have a Telkom 10GB sim with wifi router that I work off everyday using it for much for downloading and uploading and that last for at least 25 days... Please explain to me how this happened and what you are going to do to resolve the matter. There is a very, very good chance I will be changing providers as if this is your normal data pricing, it is absolutely absurd! My airtime balance was 189min and 2GB data before I started using the internet, 30min later, I was left with 59min and 0GB!!