You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Brian Martinez, want to travel from DCA to CLT. Please help me in booking my ticket.

ASSISTANT: Sure, may I know your trip dates?

USER: My trip dates are from 10/23 to 10/25.

ASSISTANT: Sorry, on these dates there is no flights available.

USER: It's ok, thank you.

ASSISTANT: Most welcome.