Head into Settings > Phone > SIM Pin. Toggle SIM Pin on. Note that you may need to contact your carrier to figure out what the default pin is if this is your first time setting this up. After entering ...

You'll need your iPhone's IMEI number if you want to unlock it and use it on a different cellular provider.

At some point in time, you may need to know your iPhone’s serial number and SIM number. And if you don’t have your own phone number memorized, well, it goes without saying that you’ll need to look ...

It may be useful to change the PIN code of a newly purchased iPhone (if the PIN is set to 0000 by default for example) or for safety reasons to protect from fraudulent use of your phone in case of ...