don't be tempted by these codes between £1-£2, the sellers are only interested in your money!
at best you will receive a code that is intended to unlock samsung phones (not necessarily your model) for 30 days so you can use your phone with a local sim card while abroad.
in the worst case scenario you will ruin your phone, problems can include:
phone won't accept ANY sim card
permanent white screen
phone won't turn on
serial number changed to all zero's
YOU HAVE BEEN WARNED!!!