All been said above.Ring a couple of minutes before the hour or half hour . Don't keep ringing all day if not getting an answer Try the following day .Ask if the appointment is made if it needs to be confirmed in some way .Keep your phone call short and to the point and get more info on the "profile".Get a general location for the escort where you will ring from again as the appointment is due but do not initially ask for an exact address. And be clear , calm and polite in your call.
I'm a lazy bugger and don't have a 2nd phone, so generally I like to send a PM just checking availability etc and then I would ring to confirm appointment etc....
But I do find it a little disappointing when you don't get an email or PM back..... maybe I'll just have to learn how to juggle 2 phones