Never call these numbers back! These criminals call blocks of numbers hoping somebody answers. Calling them back only tells them your number is a good number. They are already disregarding th e Do Not Call Registry. Do you really think they are honestly going to remove your number from their lists if you press 2? These guys are criminals. All you accomplished by pressing 2 is to guarantee that they, or another criminal they sell your phone number to will keep calling.
Best thing you can do when you get a call from an unrecognized number is not to answer. If it is a legitimate call, they will leave a message for you to call back. If they just keep calling & not leaving a message, block them. Calling them back just plays right into their hands.