The best way to handle these repeat offenders is to buy yourself one of those blow horns that you can get in any sporting good store or in any sporting good section of any retail store. The first time they call you, write the number down or remember what they are calling about, these scammers seem to be pretty consistent on calling so you really do not have to remember a number. Anyway, always give them one chance to tell them that you are on the national do not call list and that they are not supposed to be calling you and that they need to take you off of their call list. The next time they call, as soon as you recognize that they have called you once and you were polite in dealing with them before, hold the air horn to the phone and give it a good long 5 second blast and then hang up. Been there, done that and it works.
I received a call to the cell from Card Holder Services to reduce interest on my credit cards. Called twice in 2 minutes. I have no credit cards, never have. I tried to speak with a representative but after giving my first name only they hung up.
Also to DEP and Bruce---You can also try the method I used to stop their calls entirely. When the "card services" scammers learn the person they're calling is a 'time waster" that number will be removed from their robodialer list. Google my name to learn the method I used---it's very effective and also a lot of fun, if you have the time to play with them!