The first thing you have to do is to enter 12345 as the default security code. This is implemented for all the Nokia phones from this series. If the code entered appears to be incorrect, then the only solution is either Nokia Center where they have special tools and devices that can access the protected memory of the phone to reset it or visit your local phone service shop. They will also unlock it for a small fee since the process is not complicated at all, but you will require expensive hardware devices.
