I advised them that I listen to my customer first and apologize once they have finished. I then verify the issue with the customer to let them know I understand and immediately assist in all ways possible. I explained that angry customers are most likely going to give me more information to work with in getting their issue solved so in a way I consider angry customers easier to assist as I always have a bigger picture after listening to their issue. They will tell you when it happened, how often it happened, how it happened (in their experience), who else it is happening to, etc.