You cannot unlock a 3GS the traditional way as far as I know. (So no unlocking places) You can jailbreak your iPhone and unlock it that way. I got my iPhone unlocked from 02, they did mine for free since i'm on contract with them. Vodafone may have different conditions, or may not unlock it at all but take a look on their website. It's unlocked electronically so you don't need to go to a Vodafone store.