If a customer is unhappy for any reason, turning it into a positive experience for them is a great way to get their repeat business. It takes a lot of money and resources for a company to get new customers, and these people have basically come to you asking to give you their business. If you can give them a very positive experience to balance their negative one, and they leave feeling happy, they can be very loyal customers.
Be diplomatic, and instead of saying negative things about the competition or avoiding the subject, focus on the positives of your business. For example, we sell a lot of desserts at my job. Passover starts on Monday, so a lot of people call us looking for unleavened desserts. I spoke to a woman today who said this is the least appealing part of the Passover meal, because they just don’t taste good. We have an unleavened cake that’s made of layered pastry made with hazlenut flour, chocolate ganache, vanilla custard, and hazlenut praline. It is sooo good. So I described it in appetizing detail and gave her a sample, and she ended up ordering one. Now it’s up to me to make sure everything goes smoothly with her order, so I introduced myself, took down her phone number, and let her know that we carry special items during other Jewish holidays. It’s also good to follow up with customers if they complain about anything- it’s rare for a business to be proactive and check that everything is ok before the customer is angry enough to complain. I’ll keep this customer’s info on file along with some notes about her likes and dislikes, so that next time I’ll remember and offer her a better experience.