Having worked retail for a number of years in all different settings, I know that very rarely is the customer "right" from the "business eye" of things. But, the customer only sees the business through the "customer's eye" and it's important to take that into consideration.
It's about treating customers the way you'd want to be treated (we've ALL been customers with various problems on at least one time in our lives.) Excellent customer service is what keeps us going back for more...
Excellent customer service is what makes us feel like telling people we know to shop there. (And with social media these days, no business wants an upset customer on Facebook letting their 700+ "friends" know how poorly they were treated.......) Facebook or not, word gets around.
I've worked retail in every setting from fast-food, to gas station to Walmart, to Ebay & flea markets (& others). I've seen people pull stunts to get free food, saw them drive off claiming "they forgot to pay for the gas after they pumped it" (and the police brought them back), and the stuff that happens in Walmart with customer "complaints" is so crazy--it stays at Walmart. But every business insisted on making every customer that left, a HAPPY customer.
I was a seller on Ebay and I've had booths in flea markets with customers that I KNOW lied about items to get items for free (or at a discount). Businesses CAN take the cost of an item and claim it as a "business loss"...so usually, it's just "good business" to make the customer happy.
Glad everything worked out alright...usually it does.