You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I would like to meet my sister at Boston, please help me in booking a ticket from DEN to BOS.

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: May I know your journey dates?

USER: My journey dates are on Oct 19 and Oct 21.

ASSISTANT: Do you have any preferences?

USER: My budget for this trip is 500.

ASSISTANT: May I know your name?

USER: My name is Donald Scott.

ASSISTANT: Thanks for your details. There are no flights found on your data.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you.