Typically the telephone companies would bill callers to chat lines and then remit 45% of the money collected to chat line operators.
The telephone companies placed the chat line charges on a customers local phone bill.
With the progress of technology it became more practical, convenient, and economical for providers to work out of their homes.
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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.
The provider provided (say) 10 minutes of service, but got to keep all of the money (say 20 minutes).
When the Internet got relatively mature, sale of any sexual service not involving a minor could be made to anyone not a minor.
If a customer disputed a charge, the telephone company would usually “forgive” the charge but block the caller from calling any other chat lines.