How to dial USAUnited States, Canada and some Caribbean countries use the country calling code 1. Area codes in these countries are managed by the North American Numbering Plan (NANP). The North American Numbering Plan telephone numbering plan describes the allocation of phone numbers in US,Canada and Caribbeans All officially called numbering plan areas in the NANP have 3 digits. All area codes do not correspond to a geographical area. 8xx (excluding 811 and 899) with the last two digits matching, such as 800, 888, 877, 866, etc., are reserved for toll-free calls.