From Washington Post

Current federal law requires that when telemarketers make sales calls, they state their name, the company they represent, that they are calling to sell something, and how they can be reached if the consumer wants to cancel the order or complain. The rules forbid calling residences before 8 a.m. or after 9 p.m. And telemarketing firms must maintain a do-not-call list of those consumers who ask to be added to it. Anyone who documents telemarketers violating these rules can take legal action.