Good luck with that. All you likely did by responding was to verify that a human exists at the number they dialed. It also told them that you actually called back and listened to their message, further confirming that your number was a good number to keep calling, again and again. Make your job easier if your job requires you to call back any "cold calls." Ask your boss to install blocking software on your phone system. you can then google any number and see if it's ligit. If it appears on a list like this one you can safely block it and tend to other job duties instead.