You can find your phone number on an iPad associated with either its SIM card or FaceTime account, depending on your iPad's ...
If you need to find out your iPhone's carrier without a SIM card installed, you can do so through the Settings app.
You don't need a SIM card and cellular service to use most features of today's iPhones and Android phones. Most apps and services run just fine as long as you have access to WiFi, and you can even set ...