What should I do if the phone updates iOS 12. 1.4 and there is no sound in the incoming call and application prompt?

Please confirm your mobile phone model before updating. Apple's mobile phone has a mobile phone model limit every time the system is updated. If you can update the model after Apple 6, the previous one will be exempted! After the system is updated, it usually needs to be shut down and restarted to run normally! If it doesn't work, I suggest sending it to Apple's mobile phone customer service center for testing, or looking for a professional.