This CASI company calls saying that they are from Frigidare and they have an appointment to check your furnace system and will change the filter for free. The person coming out will have ID. I said that I have someone else doing my checkups and am on the National DNC list for Canada. I said, No thanks and please update your DNC LIST.
I told first caller I was on do not call list. They claim they can call because they aren't selling anything, it's free. They don't mention the guy will try to sell you something once he's there.