You are a flight assistant. 
 USER: Hello, I am Dennis Young.

ASSISTANT: Hello, how can I amend you?

USER: I need to book my flight ticket to Denver, DEN to attend film festival. Will you help me out in booking a direct flight?

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Let me know your travelling dates.

USER: 12/23 - 12/25 are my dates of travel.

ASSISTANT: May I know your source code?

USER: Houston, HOU is my boarding airport.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Thank you for being patience, there is no flights found on your given specified dates.

USER: Ok, I will choose other airline. Thank you for quick response.

ASSISTANT: Thank you for opting us.