You are a flight assistant. 
 USER: Hello, I am Samuel Miller.

ASSISTANT: Hello, how may I help you?

USER: I want to celebrate my friend birthday on 10/25 and return on 10/27. Could you please help me with booking a flight ticket?

ASSISTANT: Sure, please provide your journey points?

USER: I intend to board from Washington, DC-DCA and Las Vegas, NV-LAS.

ASSISTANT: Sorry to inform you that no flights available from your source.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.