We were having a promotion where whatever pair of frames and lenses you want will be $249.99 (as long as the price of the items together exceeds $249.99 of course). This was allowing quite large discounts, as most combined retail costs would be over $500 (everything was overpriced and we always had some sort of promotion, but that doesn't matter for this story).
One day a Lady walks in, I help her out and we sit down to finalize her costs, it goes something like this.
Me: Okay, so your total for today will be $249.99.
(I then show the customer the itemized things she will be receiving and the total cost of everything. It was well over $500)
Lady: I don't want the $30 anti-reflective coating, please remove that.
(I remove the coating from her order, which, for the sake of argument, brings her before promotion total down to $470 or so. Still well above our promotional price of $249.99)
Me: Okay, I took it off for you. Your total for today is $249.99
Lady: No.. I had the anti-reflective coating removed. So it should be $219.99
(I look at her, dumbfounded by the stupidity of the statement but remain calm)
Me: No ma'm, since the total costs of your items still exceeds our promotion price your total is still $249.99
Lady: But I don't want the anti-reflective coating! You're charging me $30 for something I don't want!
Me: Ma'm, this is the promotion price regardless of what add-ons you've selected or opted out of. Since your total still far exceeds the promotion, you're getting the best price I can offer you at $249.99.
She then goes on a rampage about how it was false advertisement and I was unfairly charging her for something she didn't want. She then threatened to make a complaint to the corporate office about this. Whatever, I thought.
The Next Day
I arrive at work with a fax waiting for me. The customer made the complaint and corporate gave her a $30 refund.