I'm looking to buy an iPhone relatively soon. I've heard about jailbreaking but I have no idea what it really means. If I have an AT&T phone currently (Blackjack II), does it mean that I can place the SIM card from that into a new iPhone w//o a contract, and only pay for what my old phone (the Blackjack) would cost per month? Can you even call people with a jailbroken iPhone? I'm a no0b I know. But any help would be nice.