Called once on landline, let it ring twice, hung up and immediately called back let it ring until machine picked it up, hung up just before you'd leave message. Has done this 4 times this morning already. No idea who it is and can't find number of person/who it is. I live in Evanston IL but area code is: Major Cities in Area Code 815
Belvidere, IL
Crystal Lake, IL
De Kalb, IL
Freeport, IL
Joliet, IL
Kankakee, IL
Loves Park, IL
Machesney Park, IL
Mchenry, IL
Rockford, IL
Romeoville, IL
Woodstock, IL ... way out of any area I'd do business with, hang out in or know anyone from.
This is one of those "sign with us and lower your utility bill ___" scammer people. I don't know if they allow links on here but I found a site that allows you to put in phone numbers and I never am happy with just 1 return on those. I did find the regular Area Code as you did, then found an answer saying this area code and prefix was based in Earlville, IL ( a long way South of here in the cornfields and a very nice town if I say so myself.) I then found that this number is a VoIP line based in Chicago (go to reverse telephone directory info dot com) which is part of the telephone system of "Bandwidth.com CLEC, LLC" If you look that up, (I looked at bizapedia dot com as well as their own site, which sells these massive VoIP packs for telemarketers and scumbags....did I say that outloud? :D)
So I'd say the "Unavailable" gives it away but then, you never know. I have a cousin in the middle of a cow pasture in Montana who still has phones run by squirrels and she is "Unavailable" and I can't tell you what they go through to get internet IF they can even get it or afford it from time to time.
I propose a 50,000 volt button on our phones where, after 3 calls and 2 warning texts are sent to them by us telling them to stop calling, we get to zap then so they leave us alone :D