I learned a long time ago..
To use a call blocking device or service, and if the spammers get past that, I simply don't answer the phone. I used to be able to tailor my voice mail to confuse crooks too; but the phone company took that over. Needless to say, my incidence of unwanted calls disappeared for a long time and even now, I rarely get any unknown origin calls. Once in a great while I take the chance and take the call - but fortunately they are wrong number accidents from people I actually know, but don't normally communicate with. I'm taking a big chance doing that, though, because spammers can transmit fake caller IDs, and have had that capability for some time.
It also helps to have a very long voice mail answer time set, because the spammer automated system gives up sooner - once that happens, that number goes into a "never call again" file, as a dead number - which is just gravy for me! In fact the original blocking service does that anyway to robot callers; only determined human callers get through. I sincerely hope the spammers don't discover a way to get past the signaling the blocking services use, because it will be all bets off after that.