Don't try to guess your SIM PIN. The wrong guess can permanently lock your SIM card, which means that you would need a new SIM card.
Never try to guess a SIM PIN or PUK code.* The wrong guess can permanently lock your SIM card, and then you would need a new SIM card.
Lock your SIM card with a PIN (personal identification number) to require an identification code for phone calls and cellular-data usage.
To protect your SIM card from others using it for phone calls or cellular data, you can use a SIM PIN. Then, every time you restart your device or remove the SIM card, your SIM card will automatically lock and you'll see "Locked SIM" in the status bar.
Don't try to guess your SIM PIN. The wrong guess can permanently lock your SIM card, which means that you would need a new SIM card.
Turn your SIM PIN on or off
If you have an iPhone, go to Settings > Cellular > SIM PIN. If you have an iPad, go to Settings > Mobile Data > SIM PIN.
Turn on your SIM PIN or turn it off.
If asked, enter your SIM PIN. If you've never used one, enter the default SIM PIN from your carrier. If you don’t know the default SIM PIN, don't try to guess it. Check your carrier's customer service page or the documents that came with your wireless plan. Or you can contact your carrier.
Tap Done.
If you forgot or don't know your SIM PIN
Never try to guess a SIM PIN or PUK code.* The wrong guess can permanently lock your SIM card, and then you would need a new SIM card. If your device asks for a PIN or code that you don't know, here's what to do:
Contact the carrier that gave you the SIM card. If you aren't sure which carrier to call, remove your iPhone SIM card or iPad SIM cardand check the card for the carrier's name or logo.
Ask your carrier to help you unlock your SIM card using the default SIM PIN or PUK code.
If you can't unlock your SIM card using the SIM PIN or PUK code or if an alert says, "PUK exhausted," ask for a new SIM card.
