You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Justin Williams here. Can you please book a flight ticket from ORD to IAH?

ASSISTANT: May I know your desired travel dates please?

USER: Sure, I need to travel on dates of 12/24 and 12/26.

ASSISTANT: There is no flight available on your specified travel dates.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thank you for opting us.

USER: Most welcome.