If you aren't the ultimate... «Winning With the Customer from Hell: A Survival Guide (Winning With the . . . from Hell)»

If you aren't the ultimate decision maker, try saying something like this: "Sir, this is something my manager usually looks after, but it's very important to me that you are satisfied. If it is okay with you, I would like to get your name, telephone number, and address so that I can personally see to it that this gets resolved".