No service on iPhone 7

Review this info to see which one will help you.

If you see No Service or Searching on your iPhone or iPad - Apple Support

If you see an Update Failed or Apple Pay Not Available alert after iOS update or restart - Apple Support

Update your carrier settings on your iPhone or iPad - Apple Support

This may apply to your phone...iPhone 7 Repair Program for "No Service" Issues - Apple Support

I updated my iPhone XR to 13.3.1 & immediately the no SIM error started showing. Likewise am unable to make/receive calls or get mobile data.

I’ve tried reinserting my SIM, hard reset of my phone, reset network settings & it all doesn’t work.

Sure seems like it’s the software update bug.

What else can I do?

This may apply.

iPhone 7 Repair Program for "No Service" Issues - Apple Support

GCYW wrote:

What else can I do?

Carefully read and follow the suggestions in the response above yours.