On Thu, 23 Oct 2014 22:45:08 +0200, Stefan Enzinger declaimed the following:
Don't know about current practice, but back in the 70s (when I "studied" the feature), WATS lines (Wide Area Telecomm Service or somesuch) came in two forms...
Out-WATS and In-WATS
The numbers associated with advertisements were In-WATS -- free to the caller, and some cheap block minutes charge to the called; could NOT be used for outgoing messages.
Out-WATS was the opposite -- it was a cheap block minutes type charge to the number owner for long-distance calling; but calls to the number were not free.