You are a flight assistant. 
 USER: Hello, I am Benjamin Evans.

ASSISTANT: Hello, how may I help you?

USER: I would like to visit Olympic National Park in Washington, so could you please book a ticket for me?

ASSISTANT: Sure, I will help you. Can I have your journey dates?

USER: Sure, I would like to go on 11/21 and return back on 11/23.

ASSISTANT: Please send your airport codes.

USER: My source and destination airport codes are EWR and IAD.

ASSISTANT: Please wait for a while.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: Sorry, there is no flight available on your dates.

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome. Thank you for reaching us, have a nice day.

USER: Welcome.