I believe you are right about the Post Gazette. I also just cancelled my subscription a couple of days ago and they have already called here 3 or 4 times.
1-866 number seems to be intermittent. Talked to a real person. Telemarketers for different newspapers. Mine was regarding my pittsburgh post-gazette subscription. They are located in Plum Boro, PA. Told them I wanted removed immediately from their lists. Seemed to comply and was able to look up my information and informed me of who they were calling on behalf of.
This number has been calling and calling and only left one message before, and it wasn't even a message for me. It was someone calling someone about being taken off life insurance (obviously the wrong number). Now they just call and don't leave a message, daily calls, sometimes twice.