You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am looking to book a flight ticket to meet my friend in Dallas. Can you help me for booking a flight ticket from OAK to DFW?

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

USER: My travelling dates are Apr 15 and Apr 17.

ASSISTANT: Do you have any break in between journey?

USER: I need a single connecting flight.

ASSISTANT: Please help me with your class preference.

USER: I prefer to book a business class.

ASSISTANT: Is there any other specifications for you?

USER: My departure time is afternoon.

ASSISTANT: May I know your good name please?

USER: My name is Alexander Hall.

ASSISTANT: Sorry, no flights are available on your given requirements.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.

USER: Welcome.