State attorneys general from across the nation have teamed up to ensure that phone companies offer call-blocking tools for fake robocalls.
The service will be free for all customers' cellphones, but does not apply to traditional landline users.
Americans get nearly 5 billion robocalls every month.
The Federal Communications Commission has called on phone companies to block the unwanted calls and make sure caller ID numbers are real.
Similar legislation would have the same effect, but they are stalled due to concerns that legitimate calls could also get blocked.