network carrier for 3gs

hi
gust upgrade my phone to ios 5.1 when the i tune said there is upgrade for it .......... it works good but the network is not configured i made a jailbreak
with final one and i but ultrasn0w for it through cydia but i stel not get the net work
can anyone tell me what to do although i install the previous one 5.0.1 still same

thanks a lot for help

What baseband do you have? If you didn't block the baseband update, you could be on a baseband with no soft-unlock, which would require you to install the iPad baseband (and permanently disable your GPS, among other things) in order to be able to unlock.