It seems that I am burning through data a ton faster after switching to the Iphone 5s from the Droid Bionic. I had the 4gb for 30.00 plan, but that changed during my upgrade back to 2gb. I killed apps after done with them on the droid, and am wondering what I can do on the Iphone to get it under control ( went from 75% to 90% of quota overnight. I primarily use it to google things, check FB, and stream a radio show week day mornings via TuneIn radio for about 1/2 - 1 hour a day during my commute. I also connect to wireless at home and at work. This is my first Apple product outside of an ipod nano, so I am unsure what I can do.
Just closing the apps doesn't shut them down. They are probably still running in the background. Check this out: http://www.tuaw.com/2013/09/19/ios-7-video-tip-how-to-shut-down-running-apps/ Hope it helps!