If the customer approached me, as being upset, I would greet them with a Hi, how are u doing, then ask them, how I may help them. Let them explain to me what the issue/problem is, and try really hard to dissolve the issue/problem on my own. If I couldn't help them, page out for the manager who is on board for that day. Customers are top priority. Once the issue/problem has been taken care of, tell them to have a great day.