How can I configure an unlocked HTC Sensation XE for 3g connectivity in USA?

I bought this phone in India and brought it home to USA. In India I had no issues in connecting to 3G network but after coming back to USA I am no longer able to connect to 3G network (AT&T). I know the phone operates in a different frequency but I wanted to know if there is a way to tweak this. I got excited when I saw a similar link posted on another forum but that did not work on my phone. Any help is greatly appreciated. Thanks...