The DNC list does work. It stops the legitimate telemarketers. The illegal telemarketers/scammers are criminals who ignore the law (that's why they are criminals). To stop them use a call blocker. They're available online and start around $45.
http://800notes.com/nb/search?q=call+blockers
Also do not answer unknown calls and do not call them back. Do not engage scammers on the phone-it's a no win situation. By doing these things you will discourage repeat callers and prevent new ones and your number drops off target lists.
I may get 1 call (already blocked) every 4-5 days. It's how you handle the criminals that determines how often they call you or don't call you. Try taking control of your telephone.
**SCAM** This is a scam originating from Sri Lanka or India just like the IRS scams and the MS Windows scams. They are spoofing their numbers and using multiple numbers and calling repeatedly. Their reps have very thick Sri Lankan or Indian accents. Do not speak to them and don't bother to ask to be removed from their call list. It's not going to happen. Block all of their numbers!