If you say, it asks for the old code to change to a new one, then i can safely assume that you are not locked out of ur phone, but rather u are currently using it.
First of all, backup important data to MMC or to PC using PC Suite as you will surely lose ur data if u try the following methods:
Reset your phone to factory settings [ie. default settings] with *#7780#
Flash your phone to latest firmware version [if there is an update or the same version once more]. The details are in nokia website to update firmware.
I hope that the first method will reset ur security code to 12345.
All the best! And dont forget the code next time.
Can anyone tell me how to disable the lock code on my Nokia 6682? I can't remember my code as I haven't used it for a while and I want to change it but there's no option to do this. It asks for the old code in order to change it to a new one! Help.