Area codes 800, 844, 855, 866, 877 and 888. The area codes or prefixes 800, 844, 855, 866, 877 and 888 are used for toll free numbers in all the countries covered by the North American Numbering Plan.A toll free number is a telephone number people can call free of charge (the owner of the toll free number pays the calling charges).rea codes 800, 844, 855, 866, 877 and 888. The area codes or prefixes 800, 844, 855, 866, 877 and 888 are used for toll free numbers in all the countries covered by the North American Numbering Plan.