Losing customers isn't the only thing to worry about when there's a service failure.

You've probably seen the typical angry customer studies. The numbers change, but the gist is X percent of customers will stop doing business with a company after a service failure. While not exactly an earth shattering discovery, these studies prove that good service is good for business.

But what happens to the angry customers who continue doing business with your company? There doesn't seem to be a lot of discussion or concern about this group.

That could be a mistake.

I recently discovered this study from Dr. Venessa Funches that reveals angry customers may continue doing business with your company, but they can still find other ways to hurt you.

Here's what you need to watch out for.

How Angry Customers Punish Companies

Funches gathered data from 732 people who were asked to recall a specific customer service situation that made them angry. The respondents were then asked what they did next.

As expected, a large portion stopped doing business with the company. In this study, it was 42 percent. The remaining 58 percent still did business with the company, but many changed their buying behavior (respondents could choose multiple options):

• 35 percent reduced the amount of business they did

• 25 percent stopped buying certain products or services

• 17 percent stopped doing business with a particular location

Then there's the 25 percent of customers who said they continued doing business with a company in the same way because they felt they had to. You will see no change in buying behavior from these customers, though they may still find other ways to hurt you:

Here's what else angry customers do:

• 70 percent spread negative word-of-mouth about the company

• 60 percent complain to the company

Negative word of mouth includes a lot of things business leaders don't like to see:

• Negative online reviews (Yelp, Google My Business, Trip Advisor, etc.)

• Negative social media posts (hello viral tweet!)

• Negative stories shared with friends

Notice that not all customers complain to the business. There are many reasons that angry customers don't complain, so it's never safe to assume that no complaints means all is well.

What You Can Do About It

Funches's study discovered that broken promises were the number one source of customer anger. If I'm a customer service leader, I start there and look for trends in service failures.

Many customer service departments react to one complaint at a time. For example, I recently bought a handleset for my front door. There was a part missing and, even worse, there was no instructional manual in the box to help identify exactly which part I needed. The company's website did not have an instruction manual for this particular door handle, either.

It took a lot of back-and-forth to finally identify the missing part.

The major failure is it's been two months and those support documents still aren't on the company's website. That means countless other customers have likely struggled through the installation process.

These types of issues are preventable. Smart customer service leaders do two things on a regular basis:

• They look for icebergs that are subtle signs of bigger problems, such as the missing handleset instructions. 

• They collect aggregate data on the top causes of service failures so those issues can be quickly addressed.

Another action step is to re-engage customers after a critical incident.

Years ago, I worked as a national account manager for a company that sold business uniforms. A customer called who was pretty upset about a mistake in an order she received. I apologized for the mistake and agreed to send out the corrected uniforms at no charge.

Many customer service professionals stop there. An even better move is to follow up again once the customer has had a chance to cool off. In my case, I called the customer right after her replacement order was scheduled to arrive. My last conversation was during a moment of misery, but this time I was talking to my customer during a moment of delight.

The replacement order had arrived safely and the customer was very happy with the outcome.

Take Action!

Customer-focused companies are constantly learning from angry customers. Try to find the source of what's causing their anger and fix it.

Another tactic is to try to prevent customer anger in the first place. This short video shares a technique called the Pre-Emptive Acknowledgement to help you do that.