Disgusting Bad Attitude from Branch Manager Durban

I am a representative of a company that are retailers of aftermarket car accessories and replacements parts. We have been successfully running the business over 12 years now. A major aspect of our business is our online store through which we share relations with customers not only from South Africa, but same extends to cross border as well as internationally. We have been in business with TransNamib on our cross border orders and have enjoyed satisfactory service until today when I called in to enquire about a cross border quote which I had received via email. I spoke to Laurence Esterhuizen who supposedly is the branch manager for Durban. Disgusting the way he spoke to me. I am not in the transport business and so if a customer enquires as to the aspects of it, or a quote thereof, it is his responsibility to give an informed reply or a logical explanation. He was raising his voice and getting irritated to my questions and when I requested a breakdown of a quote/invoice he yelled and said\ do you think I am stupid you keep repeating the same thing to me"and slammed the phone down on me. I was horrified. Please take it up or run the risk of losing valued customers in the future. """