You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Michelle Allen, I want to book a flight ticket to SFO from IAD.

ASSISTANT: Sure, I am here to help you. Could you please share your travelling dates to search a flight?

USER: Sure, my travelling dates are 06/19 and 09/21.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no flight as per your requests.

USER: Not an issue, anyway thank you for the help.

ASSISTANT: Thank you for choosing us.