The Federal Trade Commission maintains a National Do Not Call Registry, a list of home and mobile phone numbers that have opted-out of receiving telemarketing calls. The list is only available to qualifying companies, such as telemarketers and service providers, who pay to access the list through the FTC's website.
Consumers can register a home or mobile phone number in the National Do Not Call Registry for free at DoNotCall.gov. Telemarketers are prohibited from calling a number on the National Do Not Call Registry that has been registered for at least 31 days. Consumers can file complaints against telemarketers who violate the Do Not Call list at the same website.