[Jason Gin] wanted to reuse the SIM card that came with a ZTE WF721 ... way backwards and determine the unlock command and its PIN code. It turns out the PIN was even being sent over the wire ...

It also ensures you receive texts that contain banking alerts, verification codes ... means a phone can only use SIM cards from a certain carrier. The lock is a PIN, which must be entered each ...

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.