Download the "Disconnect Ring Tone" and play it whenever you get a call such as this. Note there is a pause between your picking up your phone before someone answers. This is the computer determining whether it has reached a valid number. If you play the disconnect tone, the computer automatically removes you from their calling directory.
Today at lunch time I got another call from 206-496-0985. I did not answer the phone and the caller did not leave a message on my answering machine. They called on July 19, 2012 at 11:57 am. This is the second time they have called me. After the first call I filed a complaint on donotcall.gov. The caller ID just said "Washington".
These [***] keep calling on my cell phone. Did not answer again. I called back and got a taped recording saying I received a call from a commercial entity and press one to be removed. Made them repeat the message three times before I was disconnected. Called back and they repeated the same message. Three more repeats and was disconnected. I am sure I will still be called back as I did this several times before. They know they are violating the DNC list and do not seem to care.