I bought a sim free or unlocked iphone 4 from the apple store in the uk. I have used it on various network there with no hassle, aside from trimming down a regular sim into a micro-sim. And now that im going to the US i was told the ATT has monopolized the iphone there and they make you get a contract. I was wondering if there are other networks i could use besides AT&T or is there a network that provides prepaid services, i mainly need to use the 3G services. Thanks