You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: Can you please book a flight ticket from LAS to DFW?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please help me with your planned travelling dates.

USER: Sure, I have planned my travel  dates as Feb 16 and Feb 18.

ASSISTANT: Please help me with your name.

USER: Sure, myself Thomas Lopez.

ASSISTANT: Do you need a break in between your journey?

USER: I am looking for single connecting flight.

ASSISTANT: Do you have any other preferences in your journey?

USER: I would like to depart in evening time so please check with that.

ASSISTANT: Please allow me a minute.

USER: Sure but please make sure that the class must be economy class.

ASSISTANT: Thomas Lopez, I am really sorry to inform you that there are no flights available for your journey.

USER: Oh! It is sad to hear.  Anyway, thank you for your  time.

ASSISTANT: Thank you for reaching us. Have a great time.

USER: Most welcome.