Dear Manager,
Yes, I was the person who came in with a coupon with no expiration date on it that said I could have a deli sandwich for $5.99. You told me it was no longer valid. I pointed out to you that you had a very large sign in your front window that said the same thing. you doubted me, until you saw it. Do you still doubt me, as you took it down, of course not. I then asked again for the $5.99 special. You refused. Are you aware of what LOUSY CUSTOMER SERVICE that is? Are you aware that by my pointing the sign out to you that I saved you from another customer doing the same thing? Are you aware of false advertising? Are you aware that you lost a customer instead of created a customer? What do you suppose would happen if you comped me that sandwich and thanked me for pointing out the problem? And exactly how much would that cost you? Or even let me have the sandwich at $5.99 (ps. I went to Chick Filet instead)
Oh by the way, you are suppose to be the role model for your employees. Well, you are. They act as clueless as you.
I will be calling your corporate office. Have a nice day and give a thought or two to what customer service means.