https://www.bleepingcomputer.com/news/security/fcc-orders-phone-carriers-to-enforce-unlawful-robocall-blocking/

The Federal Communications Commission (FCC) announced earlier this week that phone companies are now required to filter calls from providers who haven't complied with a deadline to block illegal robocalls expired on September 28th.

They can only accept calls from voice service providers registered in the Robocall Mitigation Database who have implemented caller ID authentication technology for calls carried made over Internet Protocol (IP) networks or filed a robocall mitigation plan with the FCC.