If I get "Telstra" (or other) I tell them that they should know I don't have a computer.
Hubby is getting "NBN" on his old flip mobile and he knows to just hang up, never press any buttons.
One went on and on at him one day (yes, @AllyJay, saying he had a 'wiruss') so I grabbed the phone and did the same as @arpie does. 🤣
The home phone is never answered nowadays and my recording clearly tells them if they are legitimate to leave their name and number and we will call them - gee, no messages left ! A waste of money but Telstra does not have a standalone internet service.
As the cartoon says, it is a good mobile phone finder, though.