hello! i have an offer of trading my nexus s for an iphone 4. the iphone 4 is on att, the nexus is is on tmobile. are there any ways of unlocking the iphone 4 on the tmobile network and having 3g working on it? and how is the battery life on the iphone 4? my nexus s has pretty good battery, it lasts me a full day of heavy heavy use.. thanks!