How to make a telesales agent look stupid

I am getting more than fed up with offshore telesales companies calling my home in the evening. The score this week is "Tim Trent 3, rest of the world nil"

My current gambit is to be a little old man.

"I'm sorry young man, I am very deaf. Please speak slowly and Loudly"

"Louder, please?"

"Louder, please?"

"Louder, please?"

"Louder, please?"

I usually manage to get them yelling down the phone until they realise at last that I am probably playing with them. The air can get quite blue at that point. They are yelling from their call centre and look truly stupid.

Three so far this week.

And yes, they are fair game. My number is Telephone Preference Service registered. If they were not offshore I would be lodging complaints with the UK Information Commissioner.