I agree with that for normal people, but chuggers.. They're fair game to me!
I will say no, thankyou politely. If they then go away, fine. If not, I will be rude (though not swear).
It's the same as any sales telephone call.
"Hello, can I speak to NW please"?
"Yes, who is calling please?"
"I am calling from <company X I have no current business with>"
"Is it a sales call?"
"Yes"
"OK, then I'm afraid I am not interested, thank you"
"Thank you, goodbye".
OK with that. A not terrible little interlude on my day.
However, you increasingly get:
"Hello, can I speak to NW please"?
"Yes, who is calling please?"
"I am calling from <company X I have no current business with>"
"Is it a sales call?"
"No, it's for your information" (or similar)
"Well, I'm afraid you are a liar. Do not ever call me again or I will be taking further action, noting that I am signed up to the Telephone Preference Service and as such you are breaking the law by calling me in the first place. Bye" <slam phone down>
Be polite and truthful to me, and I will be polite and truthful back. I cannot abide liars and those who will not take a polite "no, thankyou", and I will not be civil to them.