Shortcuts (Robert Altman) starred Jennifer Jason Leigh as a phone sex worker; she'd make calls at home with her baby and husband in the room...Leigh apparently researched the part by observing some real phone sex workers.

I think there was another one called Girl 6, more recently.

A few years ago I worked as a dispatcher for one of these businesses (needed some extra money so wanted to work nights at something).I thought it would be interesting, having worked in another branch of the sex industry (stripping) for a little while.

Dispatchers answer phones, hook callers up with "entertainers", get their credit card info, tell them the rules, etc. etc.

I only stayed on for three weeks or so. It was a sham operation, I only got paid half what I was supposed to, the manager was CRAZY (she actually made some prank calls to me at home after I quit if you can believe that) and some of the stories I heard about certain callers were so disturbing or disgusting I was worried I'd get sick and despressed if I stayed on much longer. The women who worked the phones used to like to "unload" about their evenings (some worked from home but some worked in offices in the same suite I was in), so I was a captive audience unfortunately.

The thing about it is: some of the guys who are addicted to phone sex do it because they can't find (or even pay) a real live woman to do the thing they want...think about it.