Hi.
Test using a different compatible SIM card, since the PUK code lock belongs to the SIM and not to the phone, the new SIM will be initially unlocked, or will ask its own PIN code.
If the new SIM gets locked by itself, then the problem is the phone. If the problem does not occur with the new SIM, the original SIM card was defective.
If the problem happens again with a brand new SIM, then you will need first to reset the phone to factory settings. If still no luck, reinstall the phone firmware. See link below on firmware update. If you go for the upgrade, ensure that you download right firmware. Read instructions and perform procedure as explained. If done in the wrong way the firmware update may damage the phone.
Secret codes to reset and get info:
- *#06#IMEI number (International Mobile Equipment Identity).
- *#0000#Firmware version.
- #7780#Factory Reset.
- *#7370#Format phone.
Note format and factory reset will delete the files stored in the phone.
Nokia Europe - Device software update - SupportTest a different SIM card first.