I didn't answer, but disconnected a call from this number.    Looks like a nuisance type call to me, but since there are no posts about this number on 800notes or any other site that I could find,  I added this so if others are or will be getting calls from this number.    (Wouldn't be surprised if it is Heather/Rachel/John informing me about my final notice to lower my credit card rates.)  

Caller ID read "CHICAGO    IL".     Called to area code 605.