I would first give the accuser plenty time to wind down and then I'd approach them later in the day to apologize and ask if we could work this out either together or give me the direction to fix the problem.
I would access the situation and be very sympathic toward the customer and apologize. then i'd refer to our Parts Cataolg and review the problem and address it as best as possible to satisfy the customer.
What are your greatest strengths/weaknesses? STAR Interview/behavioral questions? Provide an example of an instance in which you were forced to manage a difficult client and how did you resolve/recover the situation?