Just because the area code is from Chicago doesn't meant he call originated in Chicago. Those VOIP calls can make it look they are calling from anywhere.
Everyone forgets that the DNC list is for legitimate telemarketers. There is nothing the government can do about scam artists calling from spoofed numbers. Also I don't think the DNC list applies to business numbers. My phone number is listed all over the internet and so fair game to anyone that wants to try and scam me even though I am on the DNC list. My business number is also my android cell phone - I use an app called Phone Warrior that does a good job of blocking unwanted calls after I have activated the block against them. The app also shows me how many other app users have blocked an incoming call. Before blocking I always check here for the comments. I can't afford to be blocking clients who might be vacationing here from other parts of the country.