I bought a used iphone 3g that was supposed to be unlocked and jailbroken. When I got it, it was jailbroken, the os was 4.2.1, the baseband was 06.15, and it had ultrasnow installed. When I put a sim in, it said no service. I have tried to run redsnow again and ultrasnow. When I load ultrasnow I get a message "Could not activate cellular data". I have tried to reboot the phone, I have tried to toggle the airplane settings, but alas, to no avail. I have read other threads where this message only appears once and then everything is fine. Is there some other cydia package that I need to install? Any help would be appreciated. BTW, I was able to unlock another iphone using the steps, so I know that it will work.