HELP! I have a 3GB ATT SIM card and I want to know if it will work if I put it into a new iphone!?

I am getting a brand new iphone on ebay that has never been opened. I have a 3GB SIM card that I currently use with my Blackjack. I heard the iphone only works with a 3GB SIM card, so will it work if I put my 3 GB SIM card into the iphone and it work?