You may have heard that the use of the word "they" as a singular word (to describe one person as opposed to a group of people) is increasingly common. Many transgender folks, particularly those who identify as gender non-binary (or genderfluid or genderqueer) use this term instead of she/her or he/him. This is something many companies are paying attention to. In fact, a few years ago, Facebook changed their settings to allow users to designate their pronoun - including "they" as one of the three options.
I realize this may be initially distressing for those of us who are grammar nerds (present company included), but back in 2015, the American Dialect Society named the singular "they" as Word of the Year. If you struggle with considering "they" as a singular term, remember that someone who is non-binary has elements of BOTH male and female - essentially more than one gender. If you think of "they" in this context, it makes sense.
Ashley Wylde does a great job of explaining this in their YouTube video below (see how we just used the singular they?!)
As Ashley explains, it's completely appropriate to use "they" when talking about someone whose gender is unclear. For example, if such a customer has a question that your associate can't answer, your associate may call over a supervisor and say, "Can you help me with this? I can't find their reservation." This is better than guessing someone's gender by saying, "Can you help me with this? I can't find her reservation" - then risk having guessed wrong and offending the customer. If even a well-meaning associate guesses wrong and offends the customer, this LGBT unconscious bias incident could put your brand's reputation at risk.
Why should this matter to companies with front line associates? Simply put, it's about respecting your customers', clients', guests' and patients' chosen gender expression. When 12% of those 18-34 identify under the transgender umbrella (GLAAD, 2017), it's critically important to be aware of addressing these customers appropriately.