Update: December 2021 : The following carriers have implemented call blocking using the following vendors:
AT&T - Hiya
T-Mobile (some of Sprint) - Call Transparency
Verizon - TNS
In addition to native blocking on Android and Iphone Devices, 20+ 3rd Party OTT (over the top) apps exist in the eco system.
As this technology matures, we will be adding advice and information here. In the meantime, we recommend you work with a registered telephone carrier that has direct relationships with these companies to register your phone numbers with the mobile network operator partners above.
Note: Neighborhood Spoofing or the practice of swapping DID's to evade carrier spam mitigation is no longer allowed by the carriers. See the spoofing page for more information.