Problem with Nokia 3620

I have a Nokia 3620 that receives calls, sends calls, and text messages with no problems. But I cannot give on internet. I'm on Cingular Wireless using cingular express (GPRS) and have a cingular wireless portal. I've used the settings sent by Cingular. When I go to service and Cingular Wireless bookmark, it starts with the G circling the world, then the G disappears. I do not get the cingular wireless portal menu. When I exit, I get "Quit browsing?". Evidently, I'm not getting through the portal. It appears it's the phone. Any ideas why I cannot get on the internet. I had to unlock the phone from AT&T to Cingular. Any advice would be appreciated.