Share your experience!
I have had this phone for about 3 months and as part of my contract I have 1.5GB of data usage each month. My phone seems to be using this within 2 weeks! I have tried turning the mobile data off whilst I am not using it but only seems to make it last a few extra days. Cannot seem to work out why it is using so much. Can anyone help?!
Go on Settings - Data usage. Scroll down and it will show you what has been using your data, and how much the programs have each used 
Ive deleted the apps that I dont use that use data. The only thing I really use internet for is social network sites.
It should say what has used the data. What's at the top?
Facebook, and says 68mb, but cant work out why its using 1.5gb
Another thing you could check is that Google Play is NOT set to 'auto update apps at any time' and the settings - general section.
Other than that is seems very strange... especially if it is not listed under 'data usage'.
Do you use Google Maps or Navigation at all? That seems to use loads, but I thought it would say on the settings thing.
I only have 500mb and have never got near to it, and use Facebook etc quite a bit on mobile data 
As Kaytea says, you should check the apps that are working.
I also have 500Mb/month and I never finish them. Maybe it's because I do not use facebook or twitter.
But if the phone finish with those 1.5Gb, then internet is working and you don't even realize.
Probably your battery drains also very fast?
Turn off the backup and restore option in settings for your Google account, my phone started using a horrendous amount of data after the jellybean update and this was of a night time when I had it switched to flight mode
it would seem that the phone keeps backing up constantly and chewing through your data, so even in flight mode you have to manually switch off data to 