To get a glimpse into how you think on your feet while also providing top notch service, your interviewer is posing this tricky scenario to you. As you talk about maintaining your composure and talking to them in a friendly yet profession tone, make sure you talk about the need to refer to company policies regarding this situation. Airlines do have different policies when it comes to price matching and while it isn't important to know the policies of the particular airline you are interviewing with in your interview, it is important that you point out to your interviewer that you would be aware of the policy if you were hired as their next Customer Service Agent, and that you would clearly communicate that policy to the customer. If you have been in a similar type of customer service situation in the past, don't hesitate to talk about how you handled that situation, as well.