We had this potential customer called us. He was asking about our service. The tone is very rude and impatient. At one point, he was asking a very specific question about how we do the service. We cannot explain in detail how we do our service especially to a customer we have not met. So we said "sorry we cannot explain it over the phone sir". Suddenly he mumbled and hang out the phone. Later we found out, this male customer is spreading rants and negative comments about our company on the internet. We thought he has not used our service, how can he said about the negative thing. It's just pure childish act. And we don't like this guy spreading negative comments on the internet. what can we do?