You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Elizabeth Young here. I am looking for a flight ticket with price below 200. Can you book it?

ASSISTANT: Sure, I am here to help you. Can I know your travelling dates?

USER: Ok. My travel dates for journey would be from 01/04 to 01/06.

ASSISTANT: Please provide me your exact airport codes?

USER: My airport codes for boarding the flight are IAD to BOS.

ASSISTANT: Sorry to say that, there are no flight's available based on your travelling dates.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for approaching us.