I didn't answer, but I called them back via caller ID. An automated message stated that "You visited one of our affiliated websites and are entitled to a $100 gift card..." at which point I hung up and put them on auto reject.
I answered this call. It was automated. Said it was Com Ed offering a discount if bills have been paid on time. Press 1 if I want to see if I am eligible for a discount. I normally ignore these types of calls. For the heck of it I pressed 1 and the phone rang and rang without answer on their end.
If a caller is legitimate, they'll leave a number and a message and they won't keep calling.
If the caller is a scammer, then the number may be spoofed, so if you do reach someone, it may be an innocent party or it might be a non-working number.
If the caller is a scammer and you do get a real phone number, then all you are doing is confirming that they reached a valid number - and they'll sell your number to other scammers.