Just checked my messages & I received the very same message. I'd like to call them just to find out the official company name so I can list them in my lawsuit....wishin I was a freaking lawyer!!!!! Not calling them back, however, if they decide to call me back, oh I'll answer!!! They aren't going to like me!!!!
Most likely they are overseas in India or Pakistan. There is nothing you can say to them that they haven't heard before, and you stand a much better chance of being the target of their revenge. The best thing to do is to block the calls, and report them to the IRS. https://www.treasury.gov/tigta/
Also warn all your friends and neighbors not to pay them anything and to report them as well. The more word that gets spread around the less money they will get, and that will certainly be much better revenge than simply cursing them out.