I have given lessons to my parents and some of my friends on hanging up on indian telemarketers. I dont know if it happens everywhere, but in australia there is a 2 second break before some one says 'hello madam' and thats when i hang up.
There is no reason for you to say a single word.
I have never had a call back.
I also have caller ID if i dont recogise the number or it is 'private' i dont answer the call.
If the whole world hang up on indian telemarkets before they spoke, there would be no industry and the world would be a better place.