Don't you just want to go up to the counter and tell the clerk to "pay attention?"
Well, when you are in business you need to make sure that you are "paying attention" to the clients. There are times that they may have tried to build up their courage to talk with you about something that has upset them and if you keep ignoring them or put your attention on other things when they are trying to talk with you, there will be a consequence.
The reason that retail stores have Customer Service counters is that they expect people to have concerns. Management knows that there will be products that do not work as expected for the customers, they not only understand this, but they also have set up a process for dealing with the problems. Unfortunately, however, for whatever reason, there are some clerks who do not understand that their job is to take the sting out of the situation and also re-establish a good relationship with a disgruntled customer.
If they do succeed at this, the story will be told over and over again to friends, family and neighbours. If they don't succeed at this, the story will be told over and over again to friends, family and neighbours. You see, business is not just about marketing and making sales. It is also about recognizing that there will be problems and having a system in place that will help to deal with the problems so that person will have renewed trust and relationship with the business.
People represent the business in which they work. You, as a solo professional, are the business. It is therefore very important that you are able to work with your clients through good times and not so good times, Over the years, I have found that the person who has had a complaint but is dealt with properly becomes not only a loyal client but also is a wonderful referral source for future business. Learn to deal with unhappy clients through listening and good customer service.