You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: I am Edward Johnson, I need to book a flight ticket to IAD from LGA.

ASSISTANT: May I know your preferable journey dates please?

USER: Sure, my preferable dates are 02/09 and 09/11.

ASSISTANT: Wait for a while please.

USER: My return date got changed just now it is on 02/11.

ASSISTANT: Edward Johnson, there are no flights available with your preferences.

USER: It's ok, anyway thank you for the help.