Unlocked iphone 4s wont work on 3 (three) network

I recently had my iphone 4s unlocked. i checked online and with apple to see when the phone was unlocked. ive tried using other sim card with the phone (t-mobile and O2). the phone was originaly on vodafone. when i insert a three sim it just reads no service on the top left. ive tried getting a replacement sim with the same result. when i try to manually connect to the network it doesnt work. when I first inserted the sim card I connected it to itunes and done the necessary carrier update.