Thanks. I am using iphone but didn’t realize Samsung had that option. I couldn’t find that option on my Essential Android phone either so it must be a vendor thing.

There is a difference between unknown callers and calls from numbers not in your contact list.

Can you explain?

An "unknown caller" is typically one that has no caller ID information provided (e.g., unlisted number). However, getting a random telemarketing call from a VoIP-provided (or spoofed) local number would still come through since the caller ID information is provided, even though the number is not in your contacts list.

Unknown = caller who has chosen to hide their number, or their number is just unavailable for any other reason.

Fortunately, my carrier allows blocking such calls on NETWORK level, so they don't ever reach my phone.