I currently have a Blackjack II (3G) and pay $30/mo for unlimited data. My friend just bought the iPhone 3G and is going to sell me his iPhone 2G for a good deal. Because its an iPhone 2G can I still get the $20/mo data plan? Also, I assume I just sign up for the plan through iTunes (assuming I'm not unlocking the phone). Can I use my current 3G AT&T simcard?