You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am Carolyn Clark. I am planning to visit Houston Zoo in HOU, can you help me in booking a ticket from DTW?

ASSISTANT: Sure, can you please share your preferable travel dates?

USER: My planning dates are from 05/21 to 05/23.

ASSISTANT: Ok, let me check for the availability of flight.

USER: Please make sure that, I need a direct flight.

ASSISTANT: Carolyn, I am sorry to inform you that there is no flight available at your request.

USER: That's fine. Anyway, thank you for your help.

ASSISTANT: Thank you for opting us.