What part of "we'll get back to you" don't they understand?

Our answering machine clearly states the above message. We'll get back to you. So, why do people insist on calling again and again, never leaving messages, or leaving the SAME messages over and over again?
This is another one of my pet peeves. And now it's worse, due to the fact that we call caller ID on our phone/TV, so I see the same numbers repeating themselves. Of course, whenever I try calling them, it gives me a message stating that it is a calling centre, and they cannot be reached at that number.
When I finally do talk to these people, I usually cut them off during their sales pitch, but then they just skip down to the part of the script where they have a counter offer, or a lower interest rate.
This is when I wish we had video phones. One simple hand gesture, and the people would know how I felt.
On a side note, I have just bought Ali her birthday gift(s).
I think she'll be happy. I must say I actually enjoyed shopping today. It's rare, and I'm sure the feeling will pass, but so far I've had a fun day. I watched the Bombers practice, went shopping, listened to some good music, and then came home to the same 3 phone calls.