If you need to find out your iPhone's carrier without a SIM card installed, you can do so through the Settings app.

To find your phone number on iPhone, you can check the Settings or Phone app. You can also find it on a computer using iTunes ...

What does it mean if your iPhone is locked? If your iPhone is carrier-locked, it's only going to work with the cellular provider that locked it. However, if your iPhone isn't locked, you'll be able to ...