Hey guys... so here's the situation. My wife and I are currently using 3g's and are on the 3g att plan. My younger brother is still using the 2g and is on a 2g price plan. One of his friends wants to sell him his 8gb iphone 3g because he wants to upgrade to 16gb. If my brother buys it from him...can he just swap out the sim from his old iphone 2g and use it in the 3g without having to upgrade/renew/pay the 3g price plan from att? Since we are all on a family plan he wants to still be on the 2g price plan but use the iphone3g. If he puts in his old sim will he be able to use the 3g since it's already been unlocked by att or will they start charging him at the 3g price plan when he puts in his sim? Thanks in advance for the help.