You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I want to book a ticket from DEN to BOS. Could you book a ticket?

ASSISTANT: Can I have your journey dates?

USER: Depart date is Apr, 2 and return by Apr, 4.

ASSISTANT: Do you need any connection limit?

USER: I would prefer direct flight.

ASSISTANT: Do you need any other specifications?

USER: I would like to depart in the evening.

ASSISTANT: May I know your name?

USER: My name is Mary Adams.

ASSISTANT: There are no flights available on your required journey dates.

USER: Thanks.

ASSISTANT: Thank you for choosing us.