I shake my head when people tell me that they won't have additional charges on their phone because their carrier uses satellite or their unlimited plan covers them anywhere in the world for only $49.99/month.
It's a cell phone not a satellite phone.
These people have no idea of how cell phones operate or any real idea of what their plan is. They make these assumptions based on a three minute conversation with the person who sold them their phone.
Paul: Thanks for giving this info for people. Not turning Data off is one way you can unknowingly rack up a big bill.
If someone knows what their potential costs are then I have no problem with them using the phone as much as they want. It's their money, not mine, and they can spend it any way they want. Just don't sit next to me in the theater and give "Uncle Herman" the step by step analysis of the production show.