So you have your unique code (usually 8, 12, or 20 digits). Now, how do you use it? Do not just type it into your dialer randomly. Follow this precise sequence:
If your phone is locked to a specific carrier, you need a network unlock code to use it with a different SIM card. nokia g20 unlock code
on your keypad to get this number; the carrier will need it. Enter the Code Power off the phone. Insert a SIM card from a different carrier. Power the phone on. So you have your unique code (usually 8, 12, or 20 digits)