When people with English names and Indian accents ring me up and tell me they don't want to sell me anything but could they have my opinion on this that or the other (currently they all seem to want to know if 'm with Sky)) I tell them I have a policy of not answering questions over the phone and as often as not they hang up before I finish the spiel.
I try to be polite. I know they're doing a thankless job. I know they get shouted at a lot.
But when people ring up saying they're from Microsoft and there's a fault with my computer I tell them curtly that they're not and there isn't- and sometimes I take it a little bit further. I care less about their feelings because what they're doing is not merely annoying but downright crooked.