You want to enter your personnal unlock code on your LG HB620T, follow the instructions bellow

LG HB620T

1. Turn phone on with simcard
2. Press telephone icon at bottom of screen to bring up the phone keypad
3. Enter 2945#*620#
4. A menu will pop up, select sim unlock
5. Enter your unlock code and press ok
6. Enter your unlock code again and press ok
7. The phone will then reboot and the unlock is complete

If you need your unlock code to use your LG HB620T with another provider, you can get your unlock code on unlock-phone-online.com