Unlocking cell phones is not a big deal. All SIM unlock codes are tied to the particular device IMEI and are carrier specific. The request for that code would need to be made from the carrier that the phone was originally manufactured for.
Remember the phone has limited number of attempts to enter the unlock code and so don't lose your chances by using fake codes. The cell phone will hard lock if there are no attempts left in the cell phone.

If your operator won’t help you unlock your phone, don’t panic. Search in google you will find a lot of websites. Here are some

http://unlockgenie.com/

http://www.gsmliberty.net/