StarCode

You could have the phone companies add a new * code similar to *69 that would automatically report the last incoming phone call as a robocaller. The phone company could automatically disconnect the offending phone number if it is reported, or if it is reported more than x number of times within x amount of time (to avoid disconnecting a phone number when an annoyed person vindictively reports a legitimate caller). It would get pretty expensive having to get new phone numbers all the time so the robocallers would have to quit the practice as not cost-effective.