I have a BT phone (On a Virgin land line) which blocks all numbers not on your contact list, the caller can choose to “announce” their call, which you can accept or reject, but the scammers systems just hang up.
We've got one like that, Aunt. When I can be bothered to look back at recent calls, there are loads from overseas, lots from strange numbers with about five noughts in front, and some sort of logo which is in red and stops the blighters ever getting to us! They all get blocked at source, and the phone never even rings!
It didn't cost much and has been a godsend!
Some of the emails are interesting though, and I sometimes wish I could read Russian...