Nokia cell phones can lock their keypads automatically. This is meant to prevent unintended phone calls or text messages. After the phone is locked, you cannot access the menu, which means you cannot access any function of the phone. If you receive an incoming call while the phone's keypad is locked, you can press the "Call" key and the call will be connected. For other functions, you must unlock the keypad first.
Press any button on the keypad. The phone will ask you to press the "Unlock" key, also called the "Call" key.
Press "Call" and press "*" within 1.5 seconds.
Enter the security code, if you have assigned one. If you haven't assigned a code, your phone will unlock itself automatically.