These people aren't telesales people trying to earn a few honest bob, they're nasty, weasily scammers who would rob their own grandma of her life savings if they could, they deserve nothing but contempt. How would you feel if they relieved your mum, nan, auntie, whoever, of their life savings? Would you still be polite to them? I doubt it.
If Hans or anyone else manages to glean a modicum of amusement by dealing with them in whatever way they see fit, then good luck to them.