Calls from an unactivated number?

Just a couple minutes ago some weird number tried calling me, but I decided not to answer because I figured it was some idiot I didn't want to talk to. I didn't recognize the number, so I looked up the area code, and it turns out it was from the Chicago area, which I do live by, but I don't know anyone in chicago, nor do I ever go there. I texted the number, and I received a text back saying the number is invalid. I was really curious who called me, so I decided to call it and see who it is. It then proceeded to tell me it's not even a working number. I probably sound like a paranoid moron or something of the sort, but I just don't understand how a number that isn't even working could call me.

The number starts with 708-208-xxxx



Does anyone know how this is possible?Calls from an unactivated number?
Some numbers only allow outgoing calls. Like pay phones for example (if you can still find one that exists) My friend works for an insurance company and if you try calling her back with the number left on the caller ID it says its not a active number.Calls from an unactivated number?
I agree with the person above me