The first call gets you to the general location, such as the right block. The second call gets you the information about the room number, building number, etc.

The purpose is twofold. Most importantly, it is for our security. No call, no shows are all too common for we ladies, using a two call system makes it less likely that some stranger who backed out the session now has my speicific location. Moreover, usually the first call will get you close enough so that the provider can watch you approach to verify that you are not accompanied by unmarked cars LOL.

The second purpose though, is for even after I've met someone. Even though I no longer have the security concerns, I still prefer that they call when they are close to my location. When I get that call, that is when I know to put the 'finishing touches' on my make up, and surroundings so that when I open the door I look my best and am ready to be at my best. I like to call it my two minute drill