You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: Joseph Wilson here. Can you please book me a ticket from PHX to IAD?

ASSISTANT: Sure, can you share your trip dates?

USER: My trip dates are Sept 19th and 21st.

ASSISTANT: Do you have any preferences?

USER: No.

ASSISTANT: Sorry, there is no flight on your given dates.

USER: Ok, not an issue. Thank you for the information.

ASSISTANT: Thank you for opting us.