I wanted know if someone tried this, I have a family plan with 4 lines and two of my lines are contract-free. (unlocked already) All my phones are iPhones. But for two of my lines are still in contract which they end this year. One is a iPhone 4 and the other is a iPhone 3gs. I was wondering can I just switch sim cards to the contract free lines and have att unlock my remaining iPhones? Has anyone tried this? Thanks!