Samsung Instinkt Phone

You can simply take all the stores that the phone is locked and ask them to unlock some places, but may ask for money. I think you can call your phone provider as well, but some are not willing to do because it was free.

and then when you have unlocked your phone, you can use any SIM card you want =)

You still need the SIM card. AT & T gives the code T-Mobile will allow a phone every 90 days only customer.