Go to options, Advanced options, scroll down to SIM CARD

type mep2 (mepp2 on Pearl 81xx, 8220)

You will not see when you type a screen will open, enter code and press enter

To enter code, turn on with original sim,  go to advanced options, sim card - type mep2 (turn sideways and press menu to expose keyboard) (you won't see as you type) a hidden menu will open, enter code, then
change modes by going to settings and mobile network and to umts and 2g/3g
  enjoy phone

HTC / Pantech/ Windows Smart Phones:

Power on with invalid sim card - enter subsidy code when prompted.

Lg: 

Tg365 Neon
2945#*365# or 3845#*365# or try *#0001#code
or enter incorrect sim, it will say " insert right sim" but the left convenience key if you press it will take you to the unlock menu it will then say "sim unlock process" and "you are about to unlock your phone. Entering the unlock code incorrectly 10 times will result in the permanent lock of your phone" continue? Then presss ok and enter code

Use original sim, with the phone in standby, enter 2945#*7101#. This will activate the extra menu.
Go to: Settings>Security>SimLock> Network
Select deactivate. Enter the unlock code

Shine/Vu and most AT&T LG models:
Insert the original network SIM
Enter *#865625#
Enter the unlocking code. Press OK

Gw620
2945#*71001# ‎?or  2945#*620#


GR500 (Xenon)
1) Insert not-allowed SIM card
2) Power on the handset- phone will display "phone restricted"
3) Select "Cancel" - phone will display "phone restriction code"
4) Enter the SIM unlock code
5) Select "OK" - the handset is now successfully unlocked
or
1. insert original sim card and turn phone on.
2. Enter 2945#*9701#
3. A menu will pop up, select sim unlock
4. Enter your unlock code and press ok
5. The phone will then reboot and the unlock is complete.
or
After turning on your mobile phone, press: *#865625#
Press Yes to continue.
Enter the 16 digit Subsidy Unlock Code
Enter the 16 digit Subsidy Unlock Code, again.
Device should say: “Network Lock Deactivated”
Phone may automatically reboot

Power on with incorrect sim ( sim from a different carrier ) Enter supplied code when prompted for "Subsidy Unlock Code".

If you see the message "Contact Service Provider" this just means someone has tried a code a few times already,  just plug the charger into the phone and check the screen every so often to see if its changed and now prompting for the Subsidy Unlock Code.  Can take up to 2 hrs

PalmOne:

Power on phone with a wrong  sim inserted. When phone is powered up dial any number, it will ask you if you want to turn phone on, click yes. It will say "your phone cannot be used with this SIM card" click ok. It will say "Network Search" click cancel. using the dial pad do the following: enter *#*#code# then press dial on the screen. It will say the sim lock has been removed from your phone

Treo 680 / Centro

Power on with non-cingular simIt will then say "Your phone cannot be used with this SIM card"Click okClick dialpad tab, bottom of the screen far leftUsing stylus type *#*#code#Press the green buttonIt will then say The SIM Lock has been removed from the phone

Treo 750

Power on with NON-Cingular simUsing onscreen keyboard enter unlock codeorPower on with NON-Cingular simusing physical keyboard hold down key with large white dot ( lower left hand corner of keyboard ) while typing numbers on the keyboard

If you have a model that's not listed, one of the 2 methods below will work.
D series, P series and older models

Power on without sim, type in #0111*unlock code#

A series, C series, F series, T series, Zx series 
Power on without sim, type in #7465625*638*Unlock code#

i607 / i610 
  BlackjackPower on with incorrect sim, and when asked to enter network pin use supplied unlock code No need to hold other keys while entering code
or
Power on without sim, you will then get a message saying "SIM Failure" at the top of the screen. Click "Done"then press the green button to get into the dial pad. Type in #7465625*638*Then it will display "Enter Network Control Key" this is where you enter the 8 digit unlock code. Then click okYour phone is now unlocked

For FIDO i607/i610 JACK
Insert SIM that is Accepted (Fido SIM)
Enter #7465625*638*
Box will popup to Enter Network Control Key
Type in Supplied Unlock Code
Your Phone is now fully unlocked

Power on with cingular sim, from main screen: press the directional pad left, * key, * key, press the directional pad left ( must be done somewhat quickly ), once in unlock menu unlock the top lock with this code