Originally Posted by RChavez
If you wind up purchasing a phone pack, I highly doubt you'll manage to get it unlocked. Especially if you're a prepaid customer. However, I'm sure you can find the unlock codes on the internet somewhere.
If you buy the phone at an independent dealer (as opposed to a Vodafone company store) they may unlock it for you if you tell them you're visiting from the US and want to use your US SIM card in it when you get back.
I did this in London a few months ago. I needed a replacement phone for my T-Mobile US account, but also wanted a local UK SIM card, so at an independent retailer on Oxford Street, I bought a Nokia 3100 with a 10-pound O2 prepaid card included, all for 60 pounds. The salesman unlocked it for me right in the store so that I could also use my US SIM card with the phone.