clever thinking! That would be a bit of a loophole in their system, and if AT&T does have a 30 day period after changing responsibility it should work. As I understand it the port wouldn't go through much scrutiny, and should all process through the billing system, and not by a rep. I don't work for AT&T, but I know our billing system handles all our number ports. One thing to keep in mind though. If you change the billing responsibility, you can only port service to T-Mobile to the individual of the same name.

My advice would be to call AT&T, tell them you don't need the phone but you have a friend who might, and ask if he can cancel it if he doesn't like the phone.