You are making the mistake of allowing them to dictate the direction of the conversation. The reply for any and all opening questions is "No thanks". Doesn't matter what the question is, doesn't matter if your reply on the surface makes no sense. Your reply is "No thanks (I do not wish to talk with you)" I don't count being this abrupt as rudeness. When you are replying to a devious and manipulative question, or a flat out lie, it's all good.
"Can I interest you in..." (Straight to the point.)
"How has your day been?" (Hi, I want you to think I'm just being friendly.)
"Do you want to save money?" (Particularly devious, who's going to say no to that?)
"I'm doing a survey, I'm not selling.. " (Liar)
You can add a "goodbye" at the end of any of the above, to suit the situation or taste.