Hi, i was thinking about buying the iphone 4g with a att plan but im that sure yet. The plan is 40+20 for txing and calling and then its like $25 for web browsing. it says DataPro 2 GB for iPhone . What does it mean 2GB a months? how much is that? how much internet use would that be? and how much is 200mb? It says it costs me if i go overboard, how would i go overboard?

Thanks