"Quite a few years ago I was working at a pizza chain and I had someone call in and ask an employee if we would honor a coupon that was over a week expired. My employee told her that we couldn't honor it but he would ask me. Before he got the chance to ask me she decided to make a big fuss/was fairly disrespectful to my employee and wanted to speak to me about it directly. She complained saying it was only expired by 'a few days.' I backed what my employee had told her, we wouldn't be honoring it.
About 20 minutes later we got a call from her again and this time I had answered. She didn't make it the whole way through asking if we would honor before I told her the answer was still no. We had caller ID so I knew it was her again.
About an hour after the second call the employee who took the first call comes back to me saying there is a woman at the front of the store who wanted to speak to me about him not honoring a coupon. It was the same expired coupon. She told me that she would be going elsewhere for pizza from that point on because our service was terrible, specifically that not honoring an expired coupon for a loyal customer (I had never seen her before and we had no records of orders from her) was 'bad business.' I told her she was welcome to go elsewhere.
The ultimate kicker is that the coupon was for 50 cents off any order. It wasn't a big deal and I would have absolutely honored it had she not treated my employee like trash on the phone."