Stella, a phone scammer gives an ''opt-out'' provision only for the illusion of legitimacy. Just as when one replies in any way to email spam, the first thing any response tells the phone scammer is that yours is a functional phone number which a live person just might respond to again. That is how your phone numbers become commodities, shared with and sold off to other criminals.
Your first stops for complaints can be the FTC and attorneys general. The FTC also maintains a complaint database for eventual enforcement. Instructions are found at the bottom of the Q&A page you were meant to read during DNC registration.
Q&A: The National Do Not Call Registry
If you can find a domestic business behind your nuisance calls you may consider filing your own TCPA lawsuit. Private action is however often frustrated by how easily the scammers hide themselves behind spoofed numbers and shell companies. My comments on the alarm system dealers from two years ago in a thread linked below fills in some background, and the ''Stop Tom'' site gives you an idea of the current messy state of the problem.