It's the same as booking with the provider, you just speak with someone other than the provider.

does the screening for the provider.  The provider pays a % of her income for these services.

try this one.  Some percentage of girls dont send their own e-mails, so when you are getting all sticky and gooey with em via e-mail, you may be talking to some hairy tatooed guy that rides a Hurley

One lady I booked with had her live in female "secretary" do all of her bookings.  There are some agencies that say they are do booking only.  The line gets blurred at times.