You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I am Christopher Carter. I need to go Las Vegas to give presentation regarding online games so please help me with flight ticket booking from Dallas.

ASSISTANT: Sure, May I know the journey codes?

USER: Thank you. DFW and LAS are the airport codes of my journey locations.

ASSISTANT: Please help me with your travel dates.

USER: Sure, I have planned to travel on dates of Aug 04 and Aug 06.

ASSISTANT: Please wait a minute.

USER: Sure, take your time.

ASSISTANT: Sorry, No flights found with your preferable dates.

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

ASSISTANT: Thank you for reaching us.

USER: Most welcome.