Changing the default passcode on the LG 840g is easy. This how to will show you how to change it.
1. Go to your main menu by tapping the right most icon at the bottom of the home screen (icon with 4 squares).
2. Go to Settings.
3. Tap the Phone option
4. Tap the Security option
5. Tap the Change Codes option.
6. Tap Security Code
7. Enter the default/current passcode of 0000 (4 zeroes), then tap Ok.
8. Enter your new 4 digit passcode and top OK, repeat to confirm.