You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I am Laura Young. Please book a flight ticket from LAS to OAK.

ASSISTANT: Sure, may I know your trip dates?

USER: My travelling dates are from Apr 27 to Apr 29.

ASSISTANT: Do you have any requirements?

USER: I want to depart in the evening time.

ASSISTANT: May I know you class preference?

USER: I have no specified class preference.

ASSISTANT: There are no flights available on your requirements.

USER: Ok, No issues. Thank you.

ASSISTANT: Thank you for reaching us.