no service please help

Firstly, you should contact your carrier to see if there are any outages in your area. Do you have a friend who might be on the same carrier to test it for you? Does it change if you go elsewhere? Does your sim card suddenly have service in another phone? This can help identify if it is a problem with your network or Apple device with the no service message.

This article should help you, but if I can be of any further assistance please let me know.

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

If it's indeed iPhone 7 -- hardware: https://support.apple.com/iphone-7-no-service