I screen my calls and picked up this one once - it's definitely a charitible sales call. I'm not sure if it's always AMVETS or not.
This guy calls me at least twice a week and I've only answered once. His modus operandi for me is about 3-5 seconds of noisy silence followed by a hang-up.
I got several more calls from this number, so I called the number back - 330-247-4272 - and the message gave me an 800 number to call. I called to try to get my number out of their database, and this is how th automated response should work: First, make sure your Caller ID is not blocked, and dial 1-800-327-4302 and select option 9. If your caller ID is not blocked, it will read back the number and ask you to confirm (press 1.) Once you confirm, you get a message saying that it may take several days, but your number will be removed from their database. I did this tonight and will report back if I get any more calls.