You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am David Evans. Could you help me in booking a flight ticket from BOS to LAS?

ASSISTANT: Sure, can I know your travelling dates?

USER: My departure day is Oct 03, return day is Oct 05.

ASSISTANT: Do you have any particular time for departing and returning?

USER: My depart time should be morning, return time should be evening.

ASSISTANT: Would you like to prefer direct flight or connecting flight?

USER: I want a flight with one connection.

ASSISTANT: Which class do you prefer?

USER: I am comfortable with any class.

ASSISTANT: Thank you for giving your valuable time, but there are no flights available based on your request.

USER: No problem, thank you.

ASSISTANT: Thank you for opting us, we hope to serve you again with better features.