Find My iPhone is a great way to secure your iPhone in case it is lost or stolen, but it doesn’t do much to protect your SIM card. Indeed, without a PIN enabled on your SIM, anyone with access to your SIM card can use it to make phone calls, send messages, and use cellular data.
This is of course a worst case scenario that I am describing here, but securing your SIM card with a Personal Identification Number is a great way to add another level of security to your phone and make sure that even if the device itself becomes compromised, your cellular plan can remain somewhat protected.
How to set a SIM PIN on your iPhone
1) Open the Settings app, and go to Phone > SIM PIN, then enable the SIM PIN toggle.
2) If this is your first time setting up a SIM PIN, you will be required to create a new PIN containing 4 to 8 numbers. If you previously had a PIN enabled, you will have to re-enter that PIN to enable SIM protection.
How to turn off SIM PIN on your iPhone
1) Launch the Settings app, and go to Phone > SIM PIN, then disable the SIM PIN toggle.
2) Enter your PIN code in order to validate your request to disable SIM PIN, then tap Done.
What happens when SIM PIN is enabled?
Every time you reboot your iPhone, or if you insert the SIM card in a different phone, you will have to enter your SIM PIN to unlock the SIM card. As mentioned above, this is a great way to secure your SIM card and make sure that in the event someone stole your iPhone, they wouldn’t be able to re-use that SIM card in a different phone.
Be very careful not to forget that SIM PIN though, or else your SIM card will be locked and you will have to get in touch with your carrier to obtain a PUK code in order to unlock the locked SIM card.