The cell phone provided by your cellular service provider includes several security features to ensure it can't be used by unauthorized users, such as if the phone is stolen. One of those features is the ability to prevent access to the SIM card with a password. Unfortunately, the feature may backfire if you accidentally type the code incorrectly, resulting in a "blocked SIM" message. The method for unblocking the SIM depends on which password you entered incorrectly and how many times an incorrect code has been used.
Hold down your phone's power button until the device completely shuts off. Press the button again to turn the phone back on.
Check your cell phone's user manual to find the specific security password and locking code for your phone model. The security password is usually "1234" and the locking code is generally "000000."
Enter the security password first by tapping the number keys on your phone's keypad. Wait to see if the SIM block message disappears or if you receive a message stating the password was incorrect.
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Type the locking code if the SIM card remains blocked and wait to see if the message is removed from the screen. Call your cellular service provider's customer support line for assistance if the message instead changes to "PUK Lock." The customer service representative will provide you with the correct PUK code for your phone.