Just received the second call today from this number. This one at 5:16 pm and the first at 3:35 pm. They never leave a message - just continue to call which irritates the heck out of me. I'm not a DNC list so why do they keep calling?
Generally research organizations are exempt from the DNC rules. As are charities. Of course your callers may be scammers for information fishers in which case they will ignore any rules. About all you can do is invest in a call blocker and DO NOT pick up on call numbers you do not recognize.