You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I need to travel from IAD to SEA.So please help me to search a flight ticket. My travel dates are 05/19 and 05/21.

ASSISTANT: Sure, can I know the flight dates please? Ok, hold on for a moment please.

USER: Sure.

ASSISTANT: May I know your name please?

USER: I am Helen Harris.

ASSISTANT: Sorry to say this Helen, we could not find a flight on your requested dates.

USER: It's ok. Thank you.

ASSISTANT: Thank you for reaching us.