Hi
I had the same issue..No service inside my office..but Full WiFi available.
I was able to connect and browse and email without any problems..
After a few days the WiFi access stopped working..
I did Reset Network under General..in the settings..
SHUT Down the iphone(dont know if this matters)
Configured my Wifi all overe again... and Now I am Cruisin...
HTH
Gary
Sidenote:My Office WiFi shows 2 bars only..but the speed is significantly reduced than my Home network(which varies between 2 or 3)