Set the Security Code There is no device-based "security code" for the AT&T Z331. However, there is a "phone password" that can be user-defined.
Set the Phone's Password
From the standby screen, press Menu.
Select Change security codes.
Select Phone lock code.
Enter the phone's current password, then press OK. NOTE: The password is user-defined; there is no default. If a password has yet to be established, the phone will prompt for a new password to be entered and then confirmed.
Enter the desired phone password (4 to 8 digits), then press OK.