Try

Would you like to "try" this "additional" product or service?  You do or don't need or want it.

• It doesn't "benefit" you unless we "convince" you it does.
• It costs us "next to nothing" but costs you "plenty".
• You may "cancel" it at "any time" unless you can't or have trouble doing so.

The correct or proper response is:

• "No, thank you."
• "You're not welcome."

Forward or backward.