I have received a complaint from DEF Company, that
you used abusive language toward their employee when
asked to clear up a mistake on an order.
Who was at fault is of little importance, but what
is important you violated company policy and came close
to destroying a potentially profitable relationship.
There is nothing you need to say to a customer or supplier
that cannot be said politely.
I have resolved the issue with DEF Company, however
a personal apology would be appropriate and welcomed.