Unused minutes were rarely usable on a second call.
Human dispatchers — female, except for gay male phone sex — answered the advertised phone numbers, processed payment via credit card, chose who of the available performers in the dispatcher's judgment best matched the clients' fantasy (grandma, black girl, college girl, etc.), and connected the client with the provider. Either could hang up, though some services put economic pressure on providers not to do so.
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.
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.
All have some way for a provider to post a picture and some text.
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.