I'm not keen on this:

Why put negative thoughts into a prospective customer's head?
I put that through the door of every custy on my payment slip and in three years of so doing I have had two call backs. (rain guarantee)
Try putting this on your payment slip:
"If anyone complains, I will take an old chair leg, bend you over something, and pull your pants down. I will then send the video to your Mother".
I bet you wouldn't have gotten those call backs.
Us? We don't get call backs.