I use SpamBlocker for filtering (available on F-Droid) to block calls, and with at least newish Samsung there is an option to hide blocked calls in the menu of

I use SpamBlocker for filtering (available on F-Droid) to block calls, and with at least newish Samsung there is an option to hide blocked calls in the menu of the phone app. I've got it configured to block on a country basis, with previous calls and contacts as a whitelist - that works for me.