this is a junk call number and they are trying to validate your number. I called it back and it says "hit 1" to be taken off list. I am on Do Not call list - so this is clearly attempt to ID # as live.
Ugh, this caller is relentless, multiple calls a day for days! Sick of it, I finally found a helpful blog comment to call 866-246-7196. Just give the caller's phone number to confirm it's on their list and the receiving phone number to add to the do not call list. Quick and easy :)