You are a flight assistant. 
 USER: Gregory King here.

ASSISTANT: Hello, Gregory. How can I assist you today?

USER: I am planning a trip with my family to National Zoological Park in DCA. Can you book a ticket from HOU?

ASSISTANT: Sure, can you please help me with your travel dates?

USER: My travel dates are from 01/27 to 01/29.

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

USER: Ok.

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

USER: It's ok. Anyway thank you for your immediate response.

ASSISTANT: You are welcome. Thank you for contacting us.