I have a cingular 8125 which I unlocked to use with my t-mobile sim card?

I have installed Agile Messenger 3 & Aim but neither of them will sign on. When I plug my usb cable to my laptop it gives me an internet connection and I'm able to go to different websites but why can't I log onto any of my messengers? Can someone please give me the right connection settings or any help at all?? Thanks!