You are a flight assistant. 
 USER: Hello, I am Lisa Collins.

ASSISTANT: Hello, how may I help you at this moment?

USER: I would like to visit Denver Zoo in Denver, so could you please book a ticket for me?

ASSISTANT: Sure. Please share your travelling dates.

USER: I would like to go on 12/24 and return back on 12/26.

ASSISTANT: Can I have your nearby airport codes?

USER: My source and destination airport codes are HOU and DEN.

ASSISTANT: Please wait for a moment.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: Sorry, there is no flights running on your required dates.

USER: That's ok, thank you for checking the availability.

ASSISTANT: Thank you for reaching us.

USER: Welcome.