To All,
A general word about "codes" to unlock anything, from a DVD player, to Satellite decoder, to cell phones: DO NOT PAY A CENT, it is just "knowledge". ANd you can get this knowledge by searching the Internet.
Type your phone model with "unlock" or "sim-lock" in Google, weed-out the guys who want to make a buck by selling you a code, and usually you will find the answer in a forum or similar.
The same goes for iPhones from the USA (I did this twice now), but you need a little program on your PC or Mac (works on both) to flash the phone and inject it a piece of program along with the current program to just get rid of the carrier limitation. Who cares if it's legal or not, who's going to check? and how? (that was for Pascual E).
So Emma, if you feel confident with Google, try it yourself, otherwise, there is another way, the Operator. And here is the trick: tell them that you are going abroad for a few weeks, and that you will be buying a local prepaid sim card to put in your phone. They cannot prevent you form doing this nor can they refuse to unlock it. If they do, make a scene on the phone or in the store. Bring your receipt with you.
Hope that helps you Emma and others.