New iPhones come with a SIM ejector tool in the box, as long as it's included in the models available to your region (unless, of course, you have the new iPhones with eSIMs). It's a tiny metal object ...

Gently cleaning the SIM card and its tray can remove dust or debris that might be obstructing proper contact. Switching Airplane mode on and off can help reset network connections and prompt the ...