If O2 has a Nokia 6600 in their portfolio, then the settings for the 6600 will do; they are based on the same Series 60 2.0 and Symbian OS 7.0s versions. You can also try to get the settings from Nokia's support pages: http://www.nokia.com/nokia/0,,71993,00.html
Has anyone been successful getting a Panasonic X800 (or X700) to connect to Cingular GPRS in the US? I have spent a lot of time on the phone with customer support (they were surprisingly helpful, by the way) and they weren't able to figure it out.
I also downloaded the config for the Nokia 6600 from Nokia's support site, which should work since the 6600 uses the same version of Symbian/Series60 but sadly that didn't work either.
I read one successful account from an X800 user who was able to use T-Mobile's T-Zones after downloading the Nokia 6600 settings, but none for Cingular. Perhaps I should have chosen T-Mobile?
The T-MobileInternet Nokia 6600 settings work great for me (X800 in northeast Ohio); don't have T-Zones. I use access point internet3.voicestream.com as I am signed up for "TMobileInternet VPN" (I think internet2.voicestream.com is the access point for straight "TMobileInternet"). I chose T-Mobile since GPRS access is unmetered (no worrying about kilobytes downloaded, etc.) and unlimited. Is Cingular's GPRS unmetered and unlimited?