The Ericsson MiniCard (SIM card) works with mobile carriers such as AT&T and T-Mobile. If you want to switch networks, you must unlock your MiniCard. This includes obtaining a PIN Unlock Key (PUK) from your mobile carrier. Once you have a PUK code, you can use a PIN to further secure your mobile phone from unauthorised use.
Contact your mobile carrier. Request a PIN Unlock Key (PUK). Verify your full name, street address, telephone number and account number.
Enter the eight-digit PUK code. Press the "OK" button.
Enter a new PIN number. It should be between four and eight digits in length. Press the "OK" button.
Re-enter the PIN number. Press the "OK" button. You now have unlocked your Ericsson MiniCard.
Entering the PUK code 10 times incorrectly will lock your MiniCard permanently.