In reply to NathanP:
My favorite on these lines was me playing along, acting stupid (as a mac user, his windows instructions weren't working well) etc.
Finally "are you playing with me?"
"why on earth would I do that? I want to solve this problem"
we then chatted amicably about this and that...
Finally: "I'd better go - my supervisor is looking at me..." and he hung up
So they are human!