The popular standard protection service providers offer is the Personal Identification Number (PIN). This four-digit code prevents unauthorized access to the SIM card, ensuring data security.

[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.

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 ...