I have different experience,like in a call center it's hard to talk to a client whose angry and high tone of their voices but for me i always take it seriously but patient,kind and lower voice and try them to calm down,listen to their complain and make them smile in a good way. I work as a waitress in my aunt's catering service, bring the orders or the food to the guests, work fast but handle the tray perfectly without causing a mess and work in a sports and clothing stores,dealing with the customers, satisfy their needs,assist them and greet them with a smile even if the customers is angry.