Device and SIM card security
Select 
> Settings > Settings > General > Security .
To change the PIN code, select Phone and SIM card > PIN code . The new code must be 4 to 8 digits long. The PIN code protects your SIM card against unauthorised use and is provided with the SIM card. After three consecutive incorrect PIN code entries, the code is blocked, and you need to use the PUK code to unblock it before you can use the SIM card again.
To set the keypad to lock automatically after a defined period, select Phone and SIM card > Keypad autolock period .
To set a time-out period after which the device is automatically locked and can be used only if the correct lock code is entered, select Phone and SIM card > Phone autolock period . Enter the length of the time-out period in minutes, or select None to deactiveate the autolock feature. When the device is locked, you can still answer incoming calls, and calls may still be possible to the official emergency number programmed into your device.
To change the lock code, select Phone and SIM card > Lock code . The default lock code is 12345. Enter the current code and then the new code twice. The new code must be 4-255 characters long. Alphanumeric (uppercase and lowercase) characters can be used. The device notifies you if the lock code is not properly formatted.