When I first go my iPhone a few months ago, it didn't use much data at all, and I was on it very often. In the past few weeks, it has started using data like crazy. This morning, I reset the data usage in settings (which is how I keep track of it), and I checked it just a few minutes ago. It said I had used 11.9 GB today. I only have a 1 GB plan a month, so you can see how that would be a major issue. I spend 75% of my day in areas where I am connected to wifi. My push-notifications have always been disabled. I do not use apps such as Pandora and Spotify to stream music. How could it use that much data in one day????