You are a flight assistant. 
 USER: Hello, I am Mary Miller.

ASSISTANT: Hello, how can I assist you today?

USER: I would like to visit Mount Evans at Denver. Can you please book me a flight ticket with fare of 500?

ASSISTANT: Sure, can you please provide your journey dates?

USER: My journey dates are 11/04 and 11/06.

ASSISTANT: To proceed booking I need your airport codes.

USER: Ok, my airport codes are from LAS to DEN.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no flights found on your given details.

USER: Ok, not a problem. Thanks for your service.

ASSISTANT: Thank you have a good day.