Fake number. I tried calling it back from my other phone and got a recorded message that this number is not connected, so I know it has been spoofed. By now they must know I am rejecting all fake calls and on the rare occasions I do answer, I just hang up, so why do they keep trying? They have conditioned me to never believe them or speak to them, so why do they think I will believe the next call!

Spam call. I get these 1 to 2 times a day, 1 to 5 days a week. They were using the same number every day til I blocked it, then they called on a private number. I picked up because I was expecting a call from a govt dept, but it was silence, so it was some scammer checking to see if my number was active. Then they know I am blocking the number they were using before.
Since then they call again regularly using a different landline number every time. I'm blocking all numbers not in my contacts list, so I think they are trying to find if there is a time when I turn off the filter (there isn't).

If they know you are blocking them, then it is obvious that you know they are criminals, yet they keep trying day after day. Do they think the next slightly different number will fool you when the last 100 didn't? How do they expect to trick someone who already knows they are lying! probably 999 out of 1000 people know that these calls are fake, and they want the 1 in 1000, but why bother calling the other 999 again and again?

In the past when I would still sometimes answer, just for something to do, I would always tell them I am on the Do Not Call Register. Then they apologise profusely and promise to remove you from their list, but they don't remove you of course. This must be to make you think it is a different scammer calling next time. They are stupid, because if someone is on that register, then if they call anyway that person will simply be angry that they are ignoring the Do Not Call Register and will hardly reward them with a sale, so the scammer is simply wasting their own time. They would be wise to actually check the register, because the vulnerable people they are looking for will not be the ones who have joined it.