See also https://en.wikipedia.org/wiki/Traffic_pumping which has involved companies like FreeConference.com, Google Voice, and others who route calls through rural carriers using standard long distance area codes. Through a quirk of the 1996 Telecom Act (since fixed), the rural carriers were able to charge access fees of up to 20 cents a minute. The carriers had revenue sharing agreements with the companies driving the calls. Multiply this by thousands of callers, where everything is handled over VoIP by a rack of servers and it was quite lucrative.

More reading: https://www.google.com/search?q=free+conference+termination+...