A cursory search reveals that this is a cruse scam... Blocked. Here is a link that teaches you how to block these numbers on your iPhone. https://support.apple.com/en-us/HT201229

scam call - avoid

Call received at 3:57 pm EDT Thursday August 11 2016. This was a local call to me - Cary, Durham, Raleigh - North Carolina - but not in my contacts list so I did not answer it - no message was left.  I called back and got a recording stating that the survey had been completed and to press nine if I no longer wanted calls from them.