When customers complain and you know you have done all you can, is frustrating. But customers are right most of the time so really listen to what they are saying. After all they have options and so do you but who benefits from this, you, the customer or future customers?
It's you the merchant because "silent customers" can kill your business very fast. They do not argue or complain, they just leave and share their experience with several people and you have no idea. So I practice kindness with customers and people whenever possible. A little humility can go a long way, you may not know what kind of day they are having so why be difficult.
A current experience on Facebook taught me a great lesson. I have replied a FB message through my email because I was in a hurry and a lot of things to be done. I had just returned from Africa, my Mother had passed away and I went home for the funeral. I have used my business email to answer FB post, no problem from anyone except one person. She posted to let me know this was unacceptable and went on and on. So I asked her to delete me as a friend and I will do likewise because I want to stay positive. Oh, she was not done and kept going on and on.
She then offered to coach me for free! Who needs coaching here? I declined and she said she wanted to help me, I said no thanks! I found out that I was not the only person she talked to or treated that way. Had she listened to me or practiced a little kindness; she would have learned that I had lost my Mother and I was away and that was the quickest way to answer all my emails in a hurry! She lost me as a customer and my respect for her is reduced, I will not recommend anyone to go to her either, even if it's free! Treat your customers with respect and kindness and complaints are not bad, it's how they are handled and resolved. Yes, you can build solid long lasting customer relationships based on complaints.