Native phone app and Hangouts both answering calls

I have a Samsung Galaxy 7 running Android 8.0.0 using Ting on the Sprint network. I use Google Voice and Google Hangouts. When I get an incoming call on the Google Voice number, both the native phone app and Hangouts both prompt me to answer and seem to be fighting with each other. How can I get the native phone app to stay out of this and just let Hangouts answer the call? [I am fine with a setup where the native phone app never answers, even for calls to the native phone number of the phone, and I never use or give out that number. If I get a call on that number, I know it is SPAM.]