I dont know the lockcode for my nokia 6260 my mother gave me and she doesnt remember it either.

SOURCE: how to unlock lockcode

try the matercode generator first . at this webs ite (enter ur imei )
press *#06# to know ur imei
http://nfader.z-host.ru/


enter this mastrcode instaead of unlock code . if this fails only a service personal of nokia care can unlock it

SOURCE: i dont remember n73 lockcode

SIM pin code:
This is a pin code that locks the sim card until you enter the correct code. This protects your account, even
if your sim is put into another handset. To reset it you need the PUK code.
Pin Unlock Code (PUK)
If you miss keyed (or forget) your SIM Pin code, and enter the wrong one 3-5 times in a row, the sim will lock up, and you'll need to enter the unlock code to release it. You should ask your Network Service Provider for this code when you need it. Don't try to guess it, because after a few wrong guesses, the SIM card will be permanently disabled.

SOURCE: have a sprint phone that is locked dont remember

Once locked, your Sprint phone will have to be reflashed at a repair center. You might try, if you haven't already, the last four digits of your phone number.