Caller ID said "Unknown name". No one was on the line.

To file complaints go to:
"http://www.donotcall.gov"
"http://esupport.fcc.gov/complaints.htm"
"http://bandwidth.com/resources/legal/policy_violations.html"

For fun, here is a site to get recorded phone messages to download to your computer, and then play when a telemarketer calls. For example, the message will tell them that their phone has been disconnected, or that they will be charged $1.50 for tracing a call, or that your phone automatically rejects anonymous calls.
"http://www.payphone-directory.org/sounds.html"