The 'Nuclear Option' -- Block Robocalls, Spam Calls On iPhone, Android When Apps Don't Work - Forbes

There's basically two ways to stop robocalls. One works some of the time, the other, all the time.....
https://www.forbes.com/sites/brookecrothers/2019/05/12/how-to-block-and-stop-robocalls-on-iphone-android-summer-2019-apps-vs-nuclear-option/#552796fa6de2