BlackList

Just going to throw out the call/sms blocker I use and love: https://github.com/kaliturin/BlackList I have no connection to the software other than being a satisfied user. Yes, it's open source. Yes it's Android only. Yes, it's SMS app is bare-bones. And the UI is ugly. That's the tradeoff for this kind of thing. It's a shame there isn't an active development community around it making it so much better. The basics are all there and they work great. Mainly if the UI was updated, and certain "extras" were added to the SMS app (for me, that'd be emoji/smiley usage and photo upload/download) - it would be perfect. But I'm willing to put up with the "bad" to gain the "good" parts of the app.

I've been pretty happy with blacklist blocker. https://github.com/kaliturin/BlackList I had to work some magic (which I have since forgotten) to convince my S9+ to ignore this background process, else it would stop working after a few hours. The key thing that I wish it had was a quick way to allow unknown calls for a specified time. This would have been helpful when given the option of staying on hold for an extended period of time or receiving a callback - or when you get that "my connection is crap, let me call you back on another line."