While I've sat out for the iPhone, iPhone 3G, and iPhone 3GS, I was unable to get my hands on a launch-day iPhone 4 this year due to work scheduling. I was able to sell my own iPhone 3GS and purchase an iPhone 4 on eBay (yeah yeah). Well, its coming tomorrow morning and it just hit me that I have a SIM card and it has a (blank, I know, I did some searching) Micro-SIM card. Will I be able to just plug it into iTunes and activate on my account? Or will I have to actually call or go to AT&T to discuss this with them? I don't want to accidentally activate the eBay purchaser's account, since the box is still sealed. Sorry if this has been answered before. I've found questions regarding iPhone purchases based on other lines but not one like this. Thanks!