I followed instructions in the Nokia 6126 manual to the letter. It wouldn't let me enter any PIN security code and when I made a 3rd attempt, it locked up and kept asking for a PUK code. Customer service said that I've lost all of my telephone numbers because the SIM card was now invalid ("fried" as she called it"). All I wanted to do was to enter a simple 4 letter PIN code and I ended up losing ALL of my contacts. BOY AM I EVER PISSED OFF!!!