How to solve the iPhone7 exclamation point without service

First, set-general-restore network settings and see if it can be solved. If not, make an appointment for maintenance in official website and go to the nearest authorized maintenance point. Ask yourself to bring your ID card when you go, but you may not need to show it. Just bring the invoice (if any).

In addition, since iPhone 7 is insured, there may be an extra charge.