iPhone 3G flashes to tmobile won't connect to simply mobile sim.

[Dennisgarcia]

My brother has an iPhone 3G that was on tmobile recently he moved with me on my Verizon plan so he removed his sim from the old tmobile iPhone and tried to sell it today to this guy who had a simply mobile SIM card and it kept searching and searching and it wouldn't connect service to him. Am I doing something wrong that I should have done we took out the sim? Or is it his sim that doesn't work? I didn't restore anything on it or anything so the jailbreak and unlock and all that is still there.