A two call system works something like this. You initially call to set up and appointment with a lady. You will normally have to give some type of information so that you can be verified and you will have to give a phone number that you can be contacted at on the day of the appointment. On the day of the appointment, the agency or lady will call you before the appointment and give you the location. Different agencies and ladies have variations on this system, some will require that you verify that you will attend the session the morning or or the day before. Some will give you the location but will not give you the exact apartment or room number until you arrive at the location. Do your homework in making your choice, because the various systems have their own risks associated with them.