You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Helen Green.

ASSISTANT: How may I guide you today?

USER: I want to travel from DCA to SEA. Can you book a flight ticket for me?

ASSISTANT: Sure, I will wait. Can you please share your travelling dates?

USER: I want to fly on 02/26 and 02/28.

ASSISTANT: Wait for a minute.

USER: Ok, take your own time.

ASSISTANT: I am sorry to say that there is no flight found.

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

ASSISTANT: Thank you for contacting us.