As someone who has worked in various customer service fields for more than a decade and has recently started running their own business I can absolutely guarantee you that good communication is the FIRST AND FOREMOST component of good customer service. Being open, honest, ready to not just hear what the customer is saying, but listen and respond appropriately to them will turn an unhappy customer into a happy costumer, and a neutral or happy costumer into a life long repeat customer. Bad at communication is bad at customer service. A wrong product, defective product, or late delivered product are all mistakes that can happen no matter how good you are, or how well you run your business. The key to if you have good customer service is how you respond to those situations, and address it to the customer which, again, requires good, clear, and prompt communication.