Why waste both our time and yours by playing games? At least we're being paid to continue whatever charade you have in mind for us - who's paying you? Pretty counter-productive, I say.
Never respond with "lack of interest". Good telemarketers have a million and one ways to respond to that, all with "converting" you in mind. (However, I guess what you could do is to keep repeating "lack of interest" in a monotonous voice...we'll get the idea )
Hang up if you must. Usually - though not always (some telemarketers are *extremely* persistent, especially the desperate ones) - a simple "No, thanks", immediately followed by hanging up the phone will suffice. Don't put off your refusal until we've gone through our whole 5-minute spiel - your silence will be misconstrued as implicit consent/interest.
I don't consider myself as one of the more agressive telemarketers out there. IMO, the more agressive you are, the more put off the respondents are going to be, and the less likely you'll obtain a closer. As well, a lot of these agressive telemarketers make bad judgement calls - efficiency (i.e. high sales rate) is often sacrificed for a non-existent sliver of hope that ends up being an exercise in futility.
I use other methods, mostly involving my voice and telephone manner. For example, I'll talk to a 20 year-old male differently than I would to a middle-aged housewife, and even more differently than to a personal business owner.