You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: Can you help me booking a flight ticket from DCA to LAS?

ASSISTANT: Sure, please share your trip dates.

USER: I will start on 07/06 and  return on 07/08.

ASSISTANT: May I know your name?

USER: I am Frank Roberts.

ASSISTANT: Do you have any specifications?

USER: I need to depart in the evening time.

ASSISTANT: Which class do you prefer?

USER: I am comfertable with any class.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry Frank Roberts, no flights are available from DCA in the evening.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.