The customer who explains calmly often makes the real problem easier to identify.

Anger compresses information. When a complaint arrives at volume, most of the exchange goes into managing the temperature, and the details that would locate the fault, what you did, what happened, when it started, never make it across. Calm is not mainly about being nice to the person in front of you; it keeps the useful facts intact.

Next time something has gone wrong, lead with the sequence of events and what you want to happen. Say plainly that you are frustrated, then keep going. Firm and clear travels further than loud.