No signal in I phone 11 since last day

connect to power and update to iOS 14.0.1 if you have not already.

what to do If you see No Service or Searching on your iPhone or iPad

You might have to Update your carrier settings on your iPhone or iPad

If your carrier confirms that there's no issue with your account or network, but you still can't connect to a cellular network, contact Apple Support.

I’m sure they will take care of the issue for you. Good lucks!