In Canada, we have the Canadian Radio & Television Communications, an administrative tribunal that regulates and supervises broadcasting and telecommunications in the public interest. Every Canadian citizen 18 and over can request to have their phone number added to an exclusion list that forbids businesses to solicit them. Only groups that do surveys are allowed to call and it's rather easy either to refuse answering questions and block them on your phone from future calls.
Same / similar everywhere. You have to understand that a scammer doesn't care about such things, and most of the time they are not even calling from the same country.
Here is what they do:
They get a software-based telephone app, which allows you to choose your own number, area code, country code.
They spoof the originating number; what you see on Call Display is not the actual caller's number.
If they want to appear local (same area code as you, or same State / Province / etc area code) they search phone databases for un-assigned numbers. Then they use that as the displayed number, so you think it's coming from you area. It isn't.
If you complain to your Teleco, there is nothing they can do because the number is not assigned to anyone. As far as they know no-one is using it.
They often call from outside the US / Canada / wherever. For a long time calls have been originating from various Carribbean countries where labour is cheap and they are phoning long distance via the internet ... in other words no long distance charges.
They are based in those countries because the industry started there, when they were assigned an 809 area code, which North Americans often assumed was a Toll-Free call from a business. So that's were they set up shop as the various techniques have evolved, they still operate from there.
Regulators are powerless to stop them; they aren't in the same country, they don't abide by the rules anyway, and they are untraceable. Some have been known to sign up as a caller with the "Do Not Call" registries. When you do this you get a list of numbers not to call. They don't call from that country, instead they pass the list off to the off-shore calling centre. And then they call them; names and working numbers helpfully provided by the regulator.
That is why you sometimes hear complaints that someone is getting more junk calls *after* they signed up on the Do Not Call list.
Beware, some 8xx / 9xx area code numbers are used for "pay by the minute" services. Your local phone company collects on their behalf. Watch your bill.
900
976
5 and 6-digit SMS messages