I'm in the same boat...I will probably wait until November before I pick up the phone again, but I wouldn't be shy about asking again to show that you really want that date (and the current date you have just isn't good for your schedule). Program Administrators have a ton on their hands already, juggling everyone's rescheduling requests. It's easy to fall through the cracks; it has happened to me a couple times already. Of course, be extremely polite and apologetic, but you probably knew that already
And if you're interviewing at places that other people are unlikely to cancel at, then it's even more crucial to be proactive about trying to change your date and not counting on someone else to cancel...