There are two choices in every customer service interaction. You can satisfy the customer, or tell them you don’t want their business. Every single interaction boils down to those two options. Investment of time in anything other than those two realities is a waste of resources because any secondary interactions will ultimately lead back to the same place: satisfaction or elimination.
If you are satisfying customers, you are keeping your brand reputation healthy. If you are fighting with customers because of something you did (like over-billing), you are damaging your brand, and very likely losing business.
Keeping a healthy brand reputation intact costs far less than attempting to repair a damaged brand. One involves maintaining good practices, while the other goes much deeper, usually involving rooting out an infected company policy, followed by employee training, apologizing to customers, a PR campaign, a website overhaul, and a new advertising campaign. See how that adds up?