Just for theft

I'm forced to buy the Just for you data bundles because my data randomly disappears or I will get messages in the middle of the night telling me my data balance which is different to the one I had when I switched off all the apps and even turned off the data before going to sleep. So i will buy the just for you data and start surfing the web and then Il get a message telling me I have been paying R2... and the Just For You data has not been used. Today I bought the 50mb which says expires 26/09/2017, I went on Instagram next thing I get a message saying I have been paying R2 and all my airtime is gone but the 50mb is still not used. I'm constantly buying airtime and data that I'm not even using. This isn't fair