Ever needed to use a sim card/modem in a headless device which doesnt support a PIN code? (cheap chinese gsm-enabled sensors, I’m looking at you!) You can remove it with a simple AT command:
#verify pin is enabled: AT+CPIN? +CPIN: SIM PIN #disable pin: AT+CLCK="SC",0,"<PIN>" OK #(eg: AT+CLCK="SC",0,"1234") #verify: AT+CPIN? +CPIN: READY
After that, the SIM card will work without a PIN code (yes, yes, security, I know, I know, but with prepaid cards, who cares)