The do not call list is a registry of phone numbers in the United States that telemarketers are prohibited from calling in most circumstances. This list is made and controled by the National Do Not Call Registry of the Federal Trade Commission (FTC). Any consumer can contact this agency and register so that their number can be on this list, which prohibits anyone who sells, any kind of goods over the phone, to do so. If they disobey and still make the call they will be fined with a certain amount of money.
There are some exceptions in this do not call list. If a consumer has an established relationship with some charities, political organisations and companies they are allowed to call you even though there is a restriction. however, even in this case there are some rules that need to be followed. For example, they can call you and ask to make a donation, but not to try and sell something. Legally, they have the right to call 18 months after some kind of purchase from the customers side. But, if the customer asks not to be called again, the agency must honor the customers request. In this case, agencies have their own Do Not Call List.
Consumers have a good response to this list, and in a period of just a few months, the number of prohibited calls is around 30 million. However, this is not a good news for telemarketing, so many of them were forced to turn to mail marketing, which results in a lot of spam.