Warning: IF IT DOES NOT WORK. DONT TRY MORE THAN 4 TIMES. IT CAN LOCK YOUR PHONE REQUIRING MAINTENANCE.
1. Turn off your phone, put in a SIM of a different provider.
2. At the wrong card message, type *#9998*3323#. A message will pop up telling you to press exit, so hit the right soft key. Choose number 7 (or 8 or 9 will work too, I think). Your phone will reboot and your SIM will work.
3. Type *0141# and then hit call. This will give you a message saying your phone is personalized.
4. Power down your phone and insert your SIM. Then power back up your phone.
5. At the SIM pass code prompt type 00000000, that is 8 zeroes. So that will totally UNLOCK your phone."