You said it yourself - they're scum bags. The DNC does work, with legitimate companies, but it's not a call blocker so it can't keep scam artists from calling you. Only you can do that. Invest in a real call blocker or at the very least, don't answer calls from numbers you don't recognize.
I'd be interested to know who this is. I've missed two calls from them, and I don't like to call random numbers back because I'm really terrified of hearing voices I don't know over the phone. "Show me your face! Who are you!" Those things and others race through my mind as I hear the slick and grumbly voice of an evil man over the phone. "You have invaded my mind! This is now a police matter and you will regret whispering your cheap monkey talk in my ear. Die, brute!" Thank you.
I have received at least 6 calls a day from this number. I have spoken to them twice now. I told them I do not want to go back to school and I have never filled out a form online to do so. This company is driving me crazy!!!