Say I'm being unreasonable, but here's my immediate reaction: infrastructure providers, whether they're fiber or cellular, should just provide the infrastructure. Voice service should be decoupled from the physical infrastructure. It should be competitive VoIP products based on open standards. The expectation should be that I can get a phone on Verizon's network, but my phone service might be through services like Google Hangouts or Skype, but that Google Hangouts and Skype can talk to each other the same way that Gmail can send email to Office 365. Same with video calls and messenger apps, frankly.
If you start from that viewpoint, then it's not about forcing Verizon to filter calls. All the questions boil down to "What should these open standards look like?" and "How do we get people to agree to use these standards?" If you have a set of good, secure standards, then you should have better luck verifying the identity of the source of the messages, and thereby identifying abusers. You'll still have some of the same problems we have in filtering spam, but (a) if you're building these standards from the ground up with modern knowledge, we can do better than what we've done with email; and (b) if you don't like your spam filtering, you can easily switch to a different provider that does a better job, and providing a good spam filter becomes a competitive edge.
Of course, this isn't going to happen. Everyone wants to lock their users into walled gardens. Google, Microsoft, and Facebook are all trying to strong-arm users into using their services rather than giving them a free choice to use the best provider. If the web were being designed today, it would all look like the early AOL, with everyone walled into the garden that they signed up for, completely unable to access content or services unless they are offered by their ISP. It's absurd.