A dissatisfied customer who doesn’t complain won’t be a customer for long.
Think about it. What is the underlying reason behind customer complaints? Is it because the customer just wants to lash at you one last time before she goes to the competition? I doubt if that’s even true 1/3 of the time. If the customer can go straight to your competitor, what does she care about you? She’s not being paid to help you improve your product!
Remember, she’s the one paying you with the expectation that you’ll deliver as promised. When your customer complains, whether politely or with a vengeance, it’s usually because, at the back of her head, she expects to come back at least one more time in the future to purchase your product. Treat her with respect and, if possible, engage in a healthy communication process with her to learn about how you can improve your product offering. It’s the least you can do.