The Canadian National "Do Not call" list is essentially toothless, as it does not provide any REAL penalties (i.e. 20+ years in jail with no early release) for the telephone scammers who, on an individual basis, may waste a few seconds or a minute of the lives of many individuals but who, on a cumulative basis, waste entire lives with their calls. We Canadians are also kept somewhat in the dark as to what investigative powers are available (and to what agencies) to ferret out such scammers. Ditto with email spammers/scammers. It does not help any that this list is administered and maintained by Bell Canada, which has a vested financial interest in telephone usage.

Until such time as Canadians bombard their MPs with demands for tough legislation (with REAL penalties) for companies who do things like mask/spoof their caller ID, and/or whose mailboxes are perpetually full whenever you try to get your number removed, etc., there will be no change from the current mess we are in when it comes to being bugged on our own time and with our own equipment by companies who push the cost of their marketing down onto us.

If this number really does call to promote air duct cleaning, the only other option you have at this point is to call them back from another number and/or with your number blocked, arrange fictional dates/times for a duct cleaning and completely waste their time with fake appointments with fake names at fake addresses in industrial areas. That is the only way such scammers will be discouraged. (Not that I am recommending that you waste your time with that, you understand!) But until then, they will laugh and laugh, while they continue to call and call...