Toll-free telephone numbers in the North American Numbering Plan

In the North American Numbering Plan (NANP), toll-free telephone numbers have the area code prefix 800, 833, 844, 855, 866, 877, or 888. Additionally, area codes 822, 880 through 887, and 889 are reserved for toll-free use in the future.

Source: Wikipedia — Toll-free telephone numbers in the North American Numbering Plan (CC BY-SA 4.0)