I actually called back thinking it was someone inquiring about my apartment for rent and I got an automated number removal message. It told me that my phone number has been logged and will be removed from their calling list within 48 hours. Might not be a bad idea to call back...
Oh and just as a note. I called back everyone of these weird numbers. And they are all the same voice mail message saying they will remove your number from their database. Might not hurt to give it a try. And if they call again. Give em a nice mouthful.