I also endorse what the FE says.
However, when I continually receive calls from the same Company month after month after repeatedly telling them not to call I cannot accept it as just someone doing their job. This is despite being with the TPS and ex-directory.
It is at the very least an irritation as well as wasting my time.
I cured one famous double glazing firm by asking for a quote for the whole house, windows, doors, gutters, barge boards, garage door and anything else I could think of. The Rep got very excited over this and even arranged for the Manager to call at 9 am the following day.
That was when I told him to make sure the Manager has a flask and sandwiches with him because it will take all day, and when he has finished I will buy nothing but have the satisfaction of wasting his time for a change.
This not so extreme as the the Murder example, which is way over the top.
It did stop the calls.
At present I get calls to all my phones on the 3 network from someone saying he is from 3 and have i had an upgrade yet. This is on contracts that are new! They are not from 3 (I have reported the matter to 3), their manner is offensive and they will divulge no information about themselves to me unless they get further details from me. They do not even know my name.
So there are bad apples out there and alas saying no or hanging up does not alter the fact that I do not want and will not buy anything from cold calls and consider them an invasion of my privacy.