How to stop scammers with spoofed phone numbers?

For well over a week now, a very persistent scammer keeps calling me over a dozen times every day. I can put my phone on silent, but then I risk missing other calls. Blocking phone numbers doesn't work, because he uses a different phone number every time. Spam blocking apps for phones mostly rely on block lists or naive-sounding algorithms like blocking phone numbers that share the first 6 digits with yours, which is not the case here.

Is it possible to detect spoofed calls? Why is spoofing even possible in the first place? Surely the phone network it's originating from knows who is really calling. Why do they allow the caller to lie about that?