My recommendation would be for you to set very clear expectations of what type of service you want your customers to receive. Then, if needed, train your employees to deliver that level of service. When you receive complaints from customers or see a level of service provided that does not meet your expectations, you need to coach, counsel, re-train and document your actions with the employee. When that does not work, quickly fire the employee and share them with your best competitor. Unfortunately, the problem you describe, to the severity you describe it, is a leadership issue. We wish you great success in getting your problem quickly resolved.