What Is a Toll-Free Number and How Does it Work? | Federal
https://www.fcc.gov/consumers/guides/what-toll-free-number-and-how-does-it-work
WEBToll free numbers are numbers that begin with one of the following three-digit codes: 800, 888, 877, 866, 855, 844 or 833. Although 800, 888, 877, 866, 855, 844 and 833 are all toll free codes, they are not interchangeable. Dialing a number using a 1-800 prefix would reach a different recipient than dialing that number using a 1-888 prefix.
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