I tried this on iOS and it doesn’t work well because it turns off all other notifications.

While calls do get through from your contacts, you don’t get notifications for anything.

I really just want a contacts whitelist, but since that isn’t an option I use nomorobo which is a subscription service that works really well to block spam calls for $2/month. It’s an iOS app, focuses on not uploading your stuff to their servers, and doesn’t collect your call logs.

I’m saying that it doesn’t work well because Do Not Disturb blocks all notifications.

People get other notifications that they want to see besides calls though.

Dnd-priority on Android does not silence texts from known contacts, I've been forced to use it because of spam calls too.

I have an s7 and I star every important number. I use use IFTTT to enable DND automaticaly at 22.00 and disable it at 8.00. Is very convinient. I can also filter an app for example whatsapp to pass DND and ring.