We strongly recommend that you secure your mobile using a PIN code, which you should change to a number of your own choosing.
Certain devices enable you to change the PIN code directly in the phone's menu.
If this option is not available, you can change your PIN code manually:
** 04*OLD PIN*NEW PIN*NEW PIN#, then press the "call" key.
Do you prefer not to have to enter your PIN code when you switch on your mobile?
You just need to deactivate this option. But you run the risk of your SIM card being used without your authorisation. And you also run a greater risk : that everyone being able to use your mobile if it is stolen.