You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Frank Walker. I would like to travel from Fort Worth-DFW to Washington-DCA to meet my grandparents, can you help me in booking?

ASSISTANT: Ok, please tell me your departure and arrival day.

USER: I am departing on 12/20 and return on 12/22.

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

USER: That's ok, thank you for your help.

ASSISTANT: Thank you.