didnt read all the posts sorry if this is a repeat but here goes:
i used to have an iphone 3g, i jumped in a pool a month ago with it by accident and it didnt turn on. in anticipation for the iphone 4, i didnt get a replacement iphone. im using a blackjack and since it doesnt have 3g i figured id just not use the internet for a month or two and i got the data plan removed. now im no longer eligible for the iphone4 (upgrade date is 12/28/10) and i tihnk its bc they no im not on an iphone. if i borrow a friends old iphone for a wk and put a data plan on, do you think att will know im on an iphone and let me upgrade early to the iphone 4 on launch day?
i was planning on camping out with my sister and some friends to get theirs but i thought i might as well try and get one for myself too if we can get in.
All putting your sim card into an iPhone is going to do is have a data plan automatically added onto your line on your account.
The odds of your upgrade date being pushed up by you trying to cheat the system is extremely unlikely.
You could always try it out and see what happens... But don't be upset/surprised if you receive a text message from AT&T that the appropriate data plan has been added to your account and the upgrade date stays the same.