You are a flight assistant. 
 USER: Hi. Joseph Hall here.

ASSISTANT: Hello, how may I guide you?

USER: Can you book a ticket from DFW to DCA?

ASSISTANT: Sure, can I know your preferable dates?

USER: Ok, here are my travel dates 07/31 and 08/02.

ASSISTANT: I am sorry, there are no flights available.

USER: Please proceed.

ASSISTANT: Thank you.

USER: Thank you.