Straight talk sim switch from iPhone to iPhone leaves "no service"

[Zehrillia]

I am having trouble with a straight talk SIM card switch from a factory unlocked iPhone 3G with a shattered screen to an iPhone 3GS factory unlocked and jailbroken. I was told by straighttalk support that I could simply switch the sim from one phone to another since the sim is compatible but the new phone does not recognize the sim and says no service. I have installed the correct APN settings so I don't know what to do from here. Please help!!