When I cancel something, I'm fine with talking to the people. I keep an excellent log of ALL communications starting with the original purpose. I do not want them to have any excuse for delaying or diverting a cancellation request.
I use an approach like this: "When we talked, your offering sounded very nice, but I really needed time to more carefully evaluate it. Now that I (we) have looked at the whole situation, we simply cannot proceed. I'm sure you understand the need to be very cautious during these difficult economic times."
No sales pitch will get me to back down. I first obtain the full name of the person with whom I am speaking, I take notes during the conversation, and then I write it up. I also note the date, time (beginning and end ) of the call, and the number I called. If transferred, I note that information also. This way if it were ever challenged at a later time, I can show proof of these conversations, and a clear willingness to handle the process appropriately.
In the end, the easiest resolution should they not comply is to file a complaint with their state Attorney General. That office will ask if you have records of all communications. The end result could be a fraud indictment against the company !