Once the desk has confirmed your plans, a deposit turns a pencilled evening into a firm one. A standard visit to a hotel or a private residence is held with 25 percent of the fare, sent by bank transfer and taken off the total, so the remaining three quarters is all that is left for the night itself.
For overnights, events and travel bookings the deposit is 50 percent. The portion of it that covers her travel cannot be refunded, since a train ticket bought or a car already on its way is money spent whatever happens next. A serious agency works this way because it keeps faith with both sides of the evening: you can trust that her diary has been cleared for you, and she can trust that a real guest is waiting at the end of the ride.