Not real estate calls, but I was getting 15-20 robocalls a day for other crap. I can heartily recommend a Sentry 3.1 call screener. You enter the numbers you allow to get through. Other’s if human can get through by jumping acouple hoops. No robos ever. If someone gets through that you don’t want calling back they can be blocked.
On cell phone allow only contact list to get through.