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.
I receive phone calls at least 2 times a day everyday from this phone number. I have tried to call it back and all it does is ring. No one ever answers it.
I received a call from this number today and it was a guy by the name of Michael Abraham offering me a subscription to the Erie Times Newspaper. I acted interested he told me he works for a company called 'Pelstart' (which I couldn't find any information on). He also told me that his office could be reached at 814-453-4691 (an Erie, PA phone #). After getting this information I demanded my name & phone # be removed from their list.