The client's customer as an individual error. This will not happen again. The problem in this way, companies are responsible for the cost of the parts themselves.
To the customer. Answer customer as human error that will not happen again. Issues in this way, the company will be responsible for the expense that is difference itself.
The Reply to the customer that the customer is the person who will not be false to occur, the problem in this, the company will be responsible for all expenses that are part.