Same here - phone rang with caller ID "Herndon VA" - call center noise in the background but no one answered when I said hello. Gave them a few choice words and hung up then blocked the number. Gotta love my Panasonic phone with the 250-number blocking feature.
I have received calls from that number many times...I have now turned the home line into a fax line and answer it when I know who the caller is. If using a fax line and someone calls you do not want to call...the pinging of the fax sound removes your number from their system, as it recognizes it as a non working number for conversation.