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.
Details vary significantly from one platform to another, but the provider may be given a personal page on the platform to use however she (sometimes he) wishes.
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.
In concept they have a lot in common with platforms such as Ebay: the seller provides the picture(s), description, and sets the price, a percentage of which is kept by the platform.
In the sex industry, similar platforms emerged facilitating the selling of used panties and other odoriferous garments, and for "cam" video sessions, in which the customer, for a fee, can direct the woman on the video screen, and for a higher fee, have a private connection (no one can see caller or provider except each other).
Big platforms as of 2016 are Niteflirt, Talkto Me, and My Phone Site; the latter also includes provision by which a manager, with the consent of the providers, could have a virtual shop with many providers under them. Customers had a variety of payment options, and pages of providers to choose from, sometimes with voice samples available.
This is the world portrayed in Spike Lee's movie about phone sex, Girl 6.
At that time independent phone sex was more dangerous, as Lee's movie portrays.
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.