PLEASE BACK UP YOUR FILES BEFORE UNLOCKING
This will also bring the phone to default settings
1. First do a CUSTOM reset: *2767*2878#
turn off the phone
2. take out the battery and sim and put wrong network SIM and insert only a half of it,
Very important so it won't ask for network password and shows "Insert SIM" message.(possibly in a different language)
Now put the battery ,and switch the phone on .(phone shows "Insert SIM" message.)
3.push the sim fully in at this stage the phone is still asking to "Insert SIM"
4. Make a FULL reset: *2767*3855#
5. The phone should reboot working with "wrong" sim inside.
6. Make a Change the NCK password to 8 zeros by typing: *7465625*638*00000000*00000000#
7. Now Disable network lock By typing: #7465625*638*00000000#
Phone is unlocked
Just thought this may be useful for someone,
*Tested by me is successful