Complaints to the feds regarding illegal calls are noted in the Consumer Sentinel database. They do not trigger any immediate response but are helpful in defining a nuisance call problem and for punishing violators. The FTC never promised you a bullet shield from every unwanted and illegal caller. You were given a means to revoke a sales caller's permission to ring your phone. The DNC registry aids voluntary compliance with the Telemarketing Sales Rule with fines available for violators. Just as one parallel, how often are you in strict compliance with a posted highway speed limit?

None of the above was a secret when you registered. You were supposed to read about what registration does for you when you submitted your numbers.

National Do Not Call Registry Q&A
http://www.consumer.ftc.gov/articles/0108-national-do-not-call-registry

Now as to taking action, I note in this long thread that no one has described what the late night caller wants. Some business might be a spoof victim is all we're told. Different categories of caller need different approaches. Options may be limited by the nature of the calls and where they originate. Very likely the caller will have to be sued before s/he quits, and right now there is bupkiss to put into a civil complaint.