You'll need your iPhone's IMEI number if you want to unlock it and use it on a different cellular provider.
If you've ever called your carrier's customer service to activate a prepaid SIM card or troubleshoot a malfunctioning Android SIM card or iPhone SIM, then you've likely needed your ICCID number. The ...
If you need to find out your iPhone's carrier without a SIM card installed, you can do so through the Settings app.