I will be going to the USA for a couple of weeks in late summer. I am now looking for a pay-as-you-go data plan for my unlocked iPhone (1st generation). Up to 500 MB should be more than enough. Just one month contract period. Unfortunately, after having researched, I am not more confused than ever. The AT&T website is not really helping me. Sprint: No idea. Virgin Mobile: No SIM card only plans. ...? So, if you can give me some pointers, I am more than grateful.