My new iPhone 8 keeps dropping calls

I have had some locations that are absolutely horrible for service. There was one time my family plan was changed, and the signals sometimes flaked out or even showed no bars in densely populated areas where you'd think there should be solid service.

I know some people think it's a bad idea, but if you're calling at home then if you can enable Wi-Fi calling the quality is almost always better. It's essentially VoIP over Wi-Fi. It would be able to overcome busy cellular networks and even bad cellular signals.

If you can't make or receive calls on your iPhone - Apple Support

Is this is one location or everywhere? Have you tried a new SIM from your cell provider?