after updating my iphone 4s to ios5.1 no service appears all the way with no calls ... any help ?

i have an officially unlocked Iphone 4s it was working will with ios 5.01 today i found that there is a new update avialable which is 5.1 when i update my phone to it NO SERVICE appears at the upper left corner and i cann't make and recieve any calls with no carrier menu in the settings ... when i tried to check the phone details i found in thesettings... general ... about ... the carrier becames Verizon 12.0 but its not mine ... any help ?