Originally, per-minute billing was provided by phone companies (in the U. There was, from some services, an attempt to keep the caller aroused but short of orgasm, so he would spend more money.(This attitude still survives among some providers.) When public (mostly female) pressure forced the phone companies to stop providing this service to sex workers, a transition was made to a manual method: pre-paid blocks of time, 10, 30, 60 minutes, whatever the customer would pay for.Once means of transmitting payment were developed, phone sex turned into primarily a commercial activity, with customers (overwhelmingly male) and sellers (overwhelmingly female).
The incentives for providers were then reversed; rather than earning money from keeping the customer on the line (orgasm delayed), they earned more from bringing the caller to orgasm quickly, so as to move on rapidly to another call.
Unused minutes were rarely usable on a second call.
Nevertheless, phone sex should not be confused with prostitution wherein money is exchanged for real life sexual services or physical interaction.
The editor of High Society magazine, Gloria Leonard, is credited with being one of the first people to use "976 numbers", then "900 numbers" for promotional purposes and soon as a revenue stream in the adult industry.
Software platforms were custom written to handle money collection and transfer, connecting caller and sex worker though neither could see anything but the platform's phone number, and metering the connection.