I used to work for a company like this. Some of them are scams but most are legitimately trying to reduce interest rates on credit cards. People think they're on the "Do not call" list, but when you press 9, you are consenting to the call. Quit being stupid and quit pressing 9 and it will eventually take you out of the system. Just hang up when you get the call.
If you tell them you have less than $3000 outstanding credit card debt, they'll hang up on you. I'm sure this will also take you off their list, and they'll stop calling.