1. insert wrong sim card to phone. in my case, i inserted a smart buddy sim card on my sun locked phone.
2. turn it on. it will ask for a Network Code (or similiar). choose SOS (for emergency calls) and dial: *2767*3855#
-while typing you will notice that the 3855 part is masked with multiple dashes (i.e. it will appear *2767*----#).
-it will cause your phone to restart.
3. change the network code by dialing: *7465625*638*00000000*00000000# (that's 2 sets of 8 0's for you)
-if it restarts and asks you for a Network Code, key in 00000000 (eight 0's still >:D)
4. then permanently unlock the phone by dialing: #7465625*638*00000000# (still eight)
5. check the phone lock status by dialing: *#7465625#
- it should display INACTIVE on the item Network Lock
there you go! worked for me! i restarted the phone and re-inserted the sim to see if it really works, and it did! >:D
Comment if it worked for you too! >:D
8/1/2013 UPDATE:
Thank you for all the positive feedback! Glad to be of help :)
Some of you were asking why it doesn't work on your phones and honestly, i couldn't answer specifically because i never ran into any problems when i tried this fix. Anyway, here are my suggestions in case you're stuck somewhere along the tutorial...
1. make sure it's Samsung GT-E1080F Model
there are lots of other models with the SAME LOOK so please make sure that you're working on that specific model, otherwise i cannot guarantee anything.
2. make sure that you dialed the numbers CORRECTLY
3. i cannot verify if this guide is specific only to SUN LOCKED phones, but according to one comment it also worked on a SMART LOCKED phone.
that's all i can suggest. thanks for reading!
8/24/2016 UPDATE:
To those who have successfully unlocked the network but are experiencing SIM LOCK problems, try these. No guarantees though 'cos I just found these codes from a forum and haven't tried them yet.
#0111*0000000# - removes SIM Lock
or
#7465625*746*00000000# disables SIM lock