You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: William Lee here. I need to travel from LAS to DEN, can you help me in reservation?

ASSISTANT: Sure, may I know your planned trip dates?

USER: My journey dates are May 24 to 26.

ASSISTANT: Do you need any other requirements?

USER: I need a direct flight which returns in evening time.

ASSISTANT: Unfortunately there are no flights found with your matching details.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thank you for the help.