When I working for customer care you always get angry at a customer now and then depending on the response. When I was angry with a customer I will not retaliate and speak harshly to the customers. I would try my utter best to calm the customer down and reason with thus make them reason wI thought me. That was to explain the situation at hand at the particular time. If the customer didn't get clear information at that time, what I will do in order for the customer to get feedback is to ask them to call back at a certain time. Or call back the customer to assure them of what has happened with the query.