A tough customer that I've had to overcome was just recently. I am currently in charge of over 300 clients within the company that I work for. It is a very fast paced environment in which we have to work with. I did have a client that was unhappy and needing certain things with a quick ETA per se. I was able to reach out to other teams, other departments to be able to ensure that it was taken care of in a timely manner. From that point on, I have been the person that he will always call for, email to, or request to speak with when he does call in.