A Service Bureau is a company that acts as a point of entry for consumers wishing to purchase information or entertainment over the phone. They are responsible for all aspects of call processing including consumer billing and collections, IP call statistics, consumer content delivery and customer satisfaction.
The Call Center is the facilities where the Adult Fantasy calls are answered.
These are the women and men who actually deliver the fantasies. Some common names for them are "fantasy artists", "adult phone entertainers", "audio erotic performers", "phone actors" or "phone mistresses"
DNIS (Dialed Number Identification System) is an industry term that refers to any marketed phone sex number. The Service Bureau uses the DNIS as the unique way of identifying all callers.
A vanity number is a phone number that spells something, which obviously makes it easier to remember and thus more valuable.