The 866 area code is not geographically allocated in the North American Numbering Plan. It is among six area codes that are reserved for telephone callers to contact a business or individual without charge.
Besides 866, the other toll-free telephone area codes are 800, 844, 855, 877 and 888. Calls to numbers within each area code are paid by the receiving subscriber.
The Federal Communications Commission regulates toll-free numbers. The FCC rules include a mandate that such numbers be transferred when a subscriber changes service providers, a prohibition on owning more toll-free numbers than is required and a ban on selling toll-free numbers.