Rude customer service

We are selling our company vehicle, now the person who purchased the vehicle took the documents to Cathy's to help him put the vehicle in his name. The person helping the purchaser insists we as the seller give a specific document which we have never had, even when we bought the vehicle. He first emailed me, then he phoned me for these documents and was extremely rude! He did not take note of the fact that the vehicle was bought over 18 years ago, there might not have been documents back then like he insists we should have. Just rude rude rude. We have been using Cathy's for many many years, but a person in customer service like THIS, will cost a company it's clientele.