I used 600 MB of my data in less than 24 hours and I only have 2 GBs per month. Anyone know whats happening? This doesn't happen on my android, only on my Iphone. (There is about 500 for the app store yet I don't download anything from there atm)
Make sure you don't have WiFi assist turned on. If the phone considers your WiFi connection slow, it will use cellular data to make up the difference in speed.
Facebook's auto-playing videos were chewing through my wife's data. They have since been disabled.
I went through a lot of data after I got my X. I forgot I hadn't re-downloaded any music back onto my device, and all my music was streaming. Didn't realise 'til I got a warning that I'd used 80% of my data from EE.
Sounds like you may have auto-downloads switched on for the app store though, and the option to download over cellular.