If your phone is not unlocking or getting signal, PLEASE perform the backup/restore once again (above). Sometimes it takes upto 3 times to get it provisioned and unlocked. Also another solution is also trying to do another restore on another computer. Many times this has done the trick too.
What if your phone shows up as NOT ACTIVATED?
You need to use an AT&T active sim card to activate or get the last owner billing zip code & last 4 of social. Please make sure you DONT confuse UNLOCKING with Activating it. They are two different things.