Iphone 4 no service after restoring to ios 7.1.2

I have an unlocked iPhone 4 i'm since febuary 2015 today I have update from ios 7.1 to ios 7.1.2 now it stucks on hello holla screen and not activating or sim not valid but my iPhone unlocked.......... i'm from pakistan

plzzzzzzzzzzz helppppppppppppp