It's the robo survey SCAM. This is a telemarketing company that skirts the DNC list by conducting a "survey" before telling you that you've won a gift certificate or a vacation for listening to a time share or discount window installation or ??????? Reports vary as to the content of the call but they all have one thing in common: if you call back you get, "thanks for calling, the survey you were called for is now finished." Block it.
They are not "skirting the DNC" except in their own minds.
The end purpose of the call is to sell someone something, and therefore it is not exempt from the law and regulations that created the DNC list.