Under Settings - Phone says “no sim”. Help

See if this helps: If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

If you already tried (to no avail) all the steps provided in this support article:--> If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad , I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> https://locate.apple.com/choose-country-region . After checking it out, they'll give you all the available options.

Regards

Giulio

(*) You can do it:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above;
• Using the "Apple Store" app, available and downloadable from AppStore.