I ported my number to Telnyx and then wrote 75 lines or less of JS. Now I have an Allowlist that rings straight through to my phone, a way to allow all calls during a time slot, and a menu that allows random callers to connect to me ONLY if they know the first letter of my last name.

Spam calls stopped very quickly, and moreover, have not really returned even after disabling it. I got off "the list" finally.