You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am Patrick Roberts, Can you help me to book a flight ticket from DEN to DCA?

ASSISTANT: Sure Patrick, may I know your journey dates please?

USER: My travel departure date is 11/09 and return date is 11/11.

ASSISTANT: Patrick, there are no flights available at this moment.

USER: Ok, not a problem. Thank you for assisting me.

ASSISTANT: Thank you for choosing us.