Here's a link to the federal government's
complaint form. It's a good idea to execute one these each time you get called on a number you've placed on the "do not call" list --or any robo-call (they're all illegal).
Every once in a while, you see an article about some telemarketing firm being fined upwards of $100 million. My theory is that the government lets them go until the number of complaints nets them a huge fine.