iPhone 3GS, jailbroken, no longer unlocked?

Hi all, hope someone can help.
Have a 3gs, IOS 6.0, 05.13.04, jailbroken and used to be unlocked, but not anymore. I use this phone when i go overseas, as i am now, and can't seem to get it working.
The jail brake is working fine, i've reinstalled ultrasnow a few times, but unlock still not working, just says no service......any ideas?

Thanks in advance