A person who serves customers as part of his job will often encounter verbal harassment from some of the people he serves. In many cases, this abuse may be frightening, humiliating and enraging. However, only in a few cases is this verbal abuse against the law. That said, although a person's actions toward a customer service representative may not constitute a violation of the law, the representative does not need to serve the person.
The First Amendment of the U.S. Constitution provides individual's the right to freedom of speech. This means that a person has a right to use language that is profane, hostile and even frightening without fear of being arrested. This means that a person is allowed to be verbally abusive to a person who works for a company without violating a law, except in certain cases.
However, although a company may not be allowed to report a verbally abusive customer to the police, it does not have to serve a verbally abusive customer. Most businesses have the right to provide or withhold service to customers at their discretion. So long as the refusal to provide service is not based on a form of discrimination -- say, refusing service to a person because of his race -- it is legal.
However, there are a number of laws that do restrict people's ability to use threatening language. While there are no federal laws that prevent people from using threatening language -- at least toward private citizens -- many states have laws that prevent people from making threats. So, if a verbally abusive customer threatens injury to a representative of a company, then the person may be violating the law, based on the state's laws.
A company may be able to prevent verbal abuse from customers in a number of ways. For example, a company that wishes to refuse service to a customer may be allowed to order a customer to leave its premises. If the customer fails to do so, then the company may be allowed to charge the person with trespassing, depending on where the incident is taking place.