Davidm laid this down on his screen :
Some genuine callers though seem to have trouble with the instructions
to "say your name then press the .... key to get connected".
(.... means I'm not revealing it, it's actually just one key press).

# (or hash key) its no big secret. The genuine callers well are used to
the systems. The computer dialled nuisance calls never get through, the
foreign scam callers don't understand the recorded instruction, so that
blocks them to.

I have only ever had one live person nuisance caller actually get
through in three years.