You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am planning for a vacation to Washington with my friends, can you help me with booking a direct flight?

ASSISTANT: Sure, I can do that for you. May I know your travel dates?

USER: My travel dates are June 12 and June 14.

ASSISTANT: Ok, may I know your source and destination airport codes?

USER: I will fly from SEA to reach DCA.

ASSISTANT: Ok, please provide me your preferences.

USER: No.

ASSISTANT: May I know your name?

USER: I am David Hill.

ASSISTANT: David Hill, I am sorry to say you that there is no flight available as per your requirements.

USER: Ok, no issues. Thank you.

ASSISTANT: You are welcome and have a nice day.