When its clearly someone answering the phone for the escort and not the girl herself. It usually means the girl has little or no English so the potential is there to be misunderstandings on her part when you get there over the services promised.
On more than one occasion the receptionist has assured me that all was included in the price and when I arrive the escort declines some and blames the receptionist. Its in the receptionists interest to take the booking as she gets paid for that part of the deal and doesn't really have to care if there is an issue later.
Other times its worked out fine when I was initially unaware of the receptionist taking the enquiry call but its a deal breaker for me if I suspect straight off its a receptionist.