There Ya' Go
First off, we're all in the customer service industry. We all have a customer, whether it's on the outside or the person standing next to you.
I've found a gentle reminder to the sales person does more to heap ridicule and rudeness on me than help anyone become more grateful for the business I bring that establishment (which allows this person to be employed).
If it appears to be an individual person's lack of customer service skills, I call the manager of the store with specifics. If it's store-wide, I don't give specific names of clerks or cashiers because there is no sense punishing one person for following higher level managers. If that doesn't seem to help, I write the officers or owners of the company. If that doesn't help, I quit doing business with the company and I make sure that they know this and why. Sometimes they care and sometimes they don't. But withholding my money is making a statement. I never show them anger and I never stray from the facts.
What happens when you have an employee reported for poor customer service? How do you react? I first check out the facts and make sure I know exactly what (and even if) went wrong. Sadly, there are customers who's emotions lead them to take out their problems on employees for no reason. I always reply to the customer with "Let me investigate and get back to you." I thank them for caring enough to tell me and I do get back to them within a week. Even if you don't have it all done, making sure you get back to them when you say you will is important. Make sure nothing you do compounds the image of poor customer service at your company.
If your employee has actually given poor customer service, make sure the customer is apologized to personally by you and if you are allowed, offer them some consolation. You must handle the employee by your procedures. But I ask that you put some time into thinking this through. Has this employee been properly trained on the expectations of good customer service? Many front line employees are the lowest paid and the least trained and the least experienced. It is no favor to throw them into customer service without firm expectations. Do they understand they represent the entire company and their job is dependent upon repeat customers? Many new-to-the-workforce employees have not been trained on simple manners or had ramifications when they didn't use them. They simply don't know. Your training not only helps your business but it will help this employee as an individual in the real world the rest of their life.
If an experienced employee demonstrates poor customer service choices, is it time for retraining? Are they experiencing some personal issue that has bled over into their reactions? In either case, you actually proceed the same way.
With some employees, it may help them to have to apologize to the customer face-to-face. If you think this may compound the problem, don't.
Although I suggest you follow your company's policies on poor performance, remember: you are all dependent upon the person you are serving for your job. Is an employee's value to the company so great you will risk loosing that customer's business by repeated offenses? You, as a supervisor, have responsibility for everyone who works for you and their treatment of their customers. Even if the whole company is sloppy, you can and should make a difference for the company's sake, for your personal integrity, for the employee's future opportunities, for customer satisfaction and repeat business AND because you (as a Christian) are instructed to serve others well.
Romans 5:3-4 "And not only so, but we glory in tribulations also: knowing that tribulation worketh patience; and patience, experience; and experience, hope:"