Thankfully, it's still reasonably civil in Australia.
I'm always on alert if they ask - "May I speak to Mr or Mrs (Surname)"
It's either the bank or a telemarketer.
I usually say straight away I'm not interested, they say "ok, thanks for your time" and that's it. Pretty painless. I used to work for a phone company helpdesk and don't like to be slack to people just doing their job for minimum wage. At least they're working for their money right?
I do like the idea though of saying in my normal average Aussie accent "sorry, I don't speak english"
