When I worked retail, I used to go the extra mile like that for people who were kind and polite and patient. Their dogs always got the fancy bandannas at no charge when I was a dog groomer (supposed to be $6 each) and the nice customers always got first pick of my Christmas appointments as well (the ones EVERYONE wants).
One time a gentleman came in with an opened, partially used bag of dog food. He told me it was his regular brand that he always bought for his dog, but for some reason this batch had made her sick, and had the company made any changes to their formula, or was there a recall? I was of course concerned, so I told him if he was willing to wait a few minutes, I'd be happy to get on the horn with the manufacturer and speak to them. (they are a local company we dealt with a lot so it really was no big deal for me to call them). The store was dead as it was the evening lull. The man waited patiently while I called the manufacturer, spoke to them, allowed the customer to speak with them and then once the conversation was over, I refunded him his money and gave him a different type of food at no charge. (both were things we weren't really supposed to do except in the most extreme circumstances, but the guy had been so calm and patient when he had every reason to be angry that I really wanted to do him a solid).
The next day he came in and bought a few small dog cookies. I asked him if his dog was feeling better and he said she seemed to be back to her old self. I said I was glad to hear it and I gave him a chew toy for her out of a bin of give-away promo stuff we'd gotten from a food rep. He left, then came back with a cup and a bag from the Starbucks next door...he had gotten me a coffee and a piece of (delicious!) chocolate cake. He told me he was very appreciative that I'd gone to so much trouble to help him sort out his dog's food issue and that he appreciated my genuine concern for his dog, and that he really felt I'd gone above and beyond for him and his dog.