RIM :: 9300 Doesn't Work With 3G

Just bought an unlocked 9300.When I set the network mode to "3G", on the signal icon, up right corner of the phone it just shows red "SOS", can't text or call. When I change the network mode to "2G & 3G", "edge" shows up by the signal icon, can do text and call.But on the AT&T website, my area is within the dark orange, which means best coverage.how to make the 3G work?Another issue is when I try to set the email, it just showing "activation request failed, a service connection is not available" And cannot send from PIN to PIN．