> My only solution that I could think of is to have a dedicated phone line just for friends/family/work, and a second line for banking/shopping/utilities/everything else.
This fails the moment one of your "clean line" contacts downloads a sketchy app that sells all their contacts, and sells an updated list as your appear in their recent calls list - meaning it's not a one-time thing, it's for a few weeks after every time you call them.
It works if you only allow incoming calls from your contacts (e.g. whitelisted numbers) on friends/family/work line. If that number leaks, who cares? The random numbers will be blocked anyway. Probably would want to set it up so the 'public' line is silenced - just periodically check the VM box for anything important.
It seems possible, but maybe not affordable, for scammers to buy information about you and then spoof numbers of places that could/should theoretically call you. If you couple this with the potential victims on the other end being elderly you've greatly increased the risks of the attack being successful.