I saw an option in my Samsung Note 3 settings to set a pin for my SIM card. It is an AT&T phone but I'm using the straight talk carrier. I'm pretty confident the phone was never on the AT&T network through AT&T. I've tried unlocking the phone before with the IMIE number and the AT&T web service. This did not work. I tried calling AT&T but the phone IMIE number was not found in your database. I cannot access this number at this time. I have three attempts left for the PUK code. What must I do?