If I leave 3G on, on my phone, will it use up data?

[Liam Prendeville]

Possibly, yea I know this doesn't really answer anything

It really depends on what apps and operating system you have on your phone, for example my windows based phone automatically checks my email and social network every 30 mins and I also have an app that updates with the news every hour. These functions can be turned off but obviously if you miss one by accident you'll still be using data. So might just be easier to turn off your 3g altogether if you don't want to use it.

The other problem with having your 3g on all the time is that it causes your phone to seek far more often for the best connection and this in turn causes your phone to go through battery power like a hungry badger through a chicken coup.