I'm on the Do Not Call list, so they are actually criminals. They're offering debt services (which I don't need) which I assume are a scam. Any moment I'm wasting of their time is a moment they're not scamming someone else.
So there's the national do not call list which doesn't work that well, then each company has their own internal Do Not Call list. If you ask the person calling you to add them to their DNC they will and the calls will stop.
I do both, and oddly they keep coming, and file complaints with the FTC. The national list works well -- violators (if they can be found) are liable to prosecution.