This is different from a cellphone being carrier-locked, which means a phone can only use SIM cards from a certain carrier. The lock is a PIN, which must be entered each time the phone is turned ...

will be attributed to you. A four-digit SIM PIN restricts unauthorized access to the SIM card. When enabled, the PIN is required to activate the SIM card after a phone restart or re-insertion.

[Jason Gin] wanted to reuse the SIM card that came with a ZTE WF721 wireless ... Unfortunately, the terminal has no function to change the PIN and none of the defaults he tried seemed to work.

Through connected vehicles, IoT applications, and next-generation 5G networks, the evolution of SIM technology underscores ...

A PUK code is required if a GSM SIM card was locked after entering the wrong PIN code three times in a row. Entering a wrong PUK code ten times in a row disables the SIM card permanently.