When you're not connected to an AT&T hotspot, what does the network status show as? You can check in Settings (should be along the lines of Settings > About > Status), look for 'Network', 'Signal strength', 'Mobile network type', 'Service state', and 'Mobile network state'.
It's possible something got knocked around while replacing the microUSB port, and as a result the phone isn't able to connect to any mobile networks. I'd try removing, checking, and re-inserting the SIM card while the phone is off if you haven't already.
01-20-2014 01:49 PM