iPhone 3G Prepaid Activation?

[PrepaidiPhone3G]

Hi,

I recently purchased a AT&T gophone activated it and all that (because my EVO got bricked), then ended up winning an iPhone 3G (from my work in a contest). My prepaid sim unlocks the iPhone, but says "no service" when I try to make a call or send a text. The iPhone is locked to AT&T and Jailbroken. I would like to know how to make it work with the iPhone without getting a new sim. All help is appreciated!

P.S. My Go Phone is a Samsung a107

[mikerlx]

I see u mention its jailbroken so all u need to do is open Cydia and add ultrasnow 0.93 in ur search section and reboot your device.