WATS - Wide Area Telephone Service
WATS is better known to consumers as "Toll-Free" service. In reality, it is only toll-free to the dialer, as the company on the other end pays for each call. Companies who subscribe to WATS also have ANI, or Automatic Number Identification, either electronically, or on their bill each month.
WATS inbound service went live with AT&T on June 14, 1965 in Alabama for a trial service. It quickly expanded to encompass many of the exchanges for the 800 NPA (area code).
Following the divestiture of AT&T in 1984, many blocks of exchanges were forced to be handed over to MCI and Sprint. Many more blocks were simply frozen for future use.
As commerce grew throughout the 1990's, the 888 NPA was added to WATS. More may be forthcoming.