Are you forced to answer the calls in any way? If you can tolerate the phone ringing, let unknown calls get no kind of answer. I don't get a slew of pests bothering me anymore, and if I get a call or two, they're rarely heard from again since they get nothing but a phone that rings. If blocking does NOT help, it's about all you can do.
Put all your spam numbers under one contact like DO NOT ANSWER. Set your cell phone to send calls from this contact straight to voice mail. Most quit calling.