Oh sorry didn't answer your question , on the phone tell the agency the time you want your booking for and the duration , 30 or 60 mins , then when you're with Jennie , ask her about extras and the rates for them , that's how you do it.
One more thing , don't let anyone on here know the time you're booking up for, don't announce it on this forum or any other place , it's your privacy you're protecting at the end of the day, just a heads up.