I forgot my 4 digit Samsung SPH A920 lock code. How can I unlock it (GTEC)

Usually your lock code is the last 4 digits of your phone number

http://www.interweb.in/samsung-user-manual/3996-samsung-sph-a920-user-manual-guide.html

try default codes if you want unlock code
There can be many ways to Unlock your phone.
As far as i know unlocking by codes is the simple and safest way.unlock using software delete some information in memory i unlock my phone using codes ,i got codes from http://www.theunlockspot.com/samsung-a920/rs10wp9/ you can unlock your phone here
I used codes to unlock my cell phone. i had my unlock code and my phone was unlocked.
you need to specify the country and network provider

Get the unlocking code from www.mobile-unlocker.com .After that you follow the free unlocking instructions here http://www.mobileunlockguide.com/samsung-sph-m330 .This will provides the complete guidance for you.

the default lock code is the last 4 digits of the phone number, if you didn't change the lock code yourself, it should be the last 4 digits of the phone number

Is the phone on the Verizon network, if you do a *228 option 1 it will reset your lock code to the last 4 digits of your cell number. Otherwise you can take where you bought your phone and they have equipment there that can reset it for you.

last four digits of your phone number

try the last 4 digits of your cell phone number, if not i need to get the numbers at the back of your phone to unlock it for you.

Take the phone to the service provider and have them flash the phone...

Put the last 4 digits of ur phone number.If it not works it means that anyone change u r phones security settings.