How do you save data? I'm FREAKING out because I just got my iPhone yesterday morning and I got at text this morning saying I've used 50% of my data already. How can this even be? I was working and sleeping most of the time! I didn't realize you had to switch to wifi to save data, so that's been done, but I'm so scared that I'm gonna accidentally go over and end up owing a lot of money! I hate this! I was so excited for this iPhone and now I feel like if I actually use it, I'm gonna regret it! How can the data go that fast!? That doesn't seem right/possible!