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.
How do you fix locked SIM on iPhone?
How to (accidentally) lock yourself out of your SIM card
- Launch Settings on your iPhone.
- Tap Cellular.
- Select SIM PIN.
- Tap the toggle to turn SIM PIN to OFF.
- If you fail the three attempts, your iPhone will ask for a PUK Code, which you can only obtain by calling your carrier.
Why does it keep saying SIM card is locked?
The SIM card on your mobile phone will become locked if you enter an incorrect personal identification number (PIN) three times. To unlock it you must reset your PIN by entering your SIM card's unique unlock key (also called a PIN unblocking key or PUK).
