I had this number call today at 4:25 p.m., I answered with no reply from the caller, though I did notice I heard what sounded like keyboard clicks in the background - as when talking to someone who is using a computer keyboard at the same time. I called back with in 15 minutes, no one picked up and no answering service did either. It is possible it is a collector. As a note, I personally have been sending resumes off to Tech position posts on Craigslist and have noticed some complaints from others doing the same that have encountered "illigitamate" posts and possible data mining by these posters for neferious reasons. I did a Re-verse Lookup on the number over the web via Intelius.com, its there as a wireless number, but you must pay 14 dollars for the record for that number.
I got 3 calls from this # today - none answered, as I don't know anyone in area code 312, and Im tired of telemarketers. After reading the above comments, I too tried to call it back, and I got a recording saying this # isn't in service. So this is a # that is being spoofed to avoid detection: clearly either a telemarketer or collection agency.