These steps show you how to do it: Power down your phone and then insert the new SIM card. If you have multiple ... To ...

Check SIM Card in iPhone Settings: Insert the SIM into your iPhone. Once your iPhone recognizes the SIM card, it will figure out the attached phone number (if there is one). Scroll down and tap Phone.

To find this number on an iPhone, go to Settings > General ... A simple way to check if your device is unlocked is to insert ...