For one data point, spam calls pretty much stopped when I switched over to Project Fi for my carrier. Outside of that, "Do Not Disturb" 24/7, whitelist all you

For one data point, spam calls pretty much stopped when I switched over to Project Fi for my carrier. Outside of that, "Do Not Disturb" 24/7, whitelist all your contacts, change your voicemail message to "I don't check my voicemail because it's constantly spam, text me", and ignore your voicemail.