I currently have T-Mobile but I am planning on transferring to AT&T for the new iPhone. I was wondering if when I used apps that required the internet like AIM or Facebook if it used a lot of the data (Specifically AIM)? Does anyone have any of the new data plans? How do you like it? My last question is if my parents already have iPhones (for the past 2 or 3 years) can they still upgrade to the unlimited data plan? Or is it too late?