it's simple. Treat people how you want to be treated. Talk to people how you'd wanna be talked to. Look at everyone you encounter as a customer. You should offer everyone the same courtesy and concern. When you are wrong admit it and be responsible for your actions. It's so easy to be stubborn and not want to give in, but do the right thing and I promise you, you will feel so much better. How often do you get customer complaints? Normally not that often. So replace the items, give refunds, pay shipping whatever it takes. That customer will be happy and you will feel good cause you did the right thing. If you get a lot of complaints, then you better put CS as a priority and start correcting yourself cause your reputation and your business will go to chits. I always tell my staff one thing, before you say or do anything take a moment and ask yourself. Is this how I want to be treated? Is this how I want to be talked to? If the answer is NO, then don't do it.