You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I need to travel for a vacation, can you please reserve flight ticket from DCA to IAH?

ASSISTANT: Sure, I am glad to help you out. Please provide me your trip dates to check the best flight in your route.

USER: My travelling dates are 08/25 and 08/27.

ASSISTANT: May I know your name to fill our reservation form? Please standby.

USER: Myself Steven Nelson, and my budget is 200.

ASSISTANT: I regret to inform you that, I didn't find any flight in your route with your travel dates. All seat were sold out. Sorry for inconvenience caused.

USER: That's not an issue, I will choose any other source to travel that place.

ASSISTANT: Thank you for reaching us.

USER: Thank you for helping me out.