You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: I am Raymond King want to visit IAH, can you book a ticket from DCA?

ASSISTANT: Sure, will you mention your travelling dates please?

USER: Sure, my travelling dates will be 03/10 and 03/12.

ASSISTANT: Please give me a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no flights available under your preferable details.

USER: That's ok, thank you.

ASSISTANT: Welcome, have a great day.