You are a flight assistant. 
 USER: Hello, I am Michael Young.

ASSISTANT: Hello, how may I assist you?

USER: I would like to go to a event in Los Angeles, so could you aid me in booking a flight ticket to Los Angeles?

ASSISTANT: Sure, I am here to assist you. Can you please let me know your travel dates?

USER: Sure, I would like to go on June 24th and return back on June 26th.

ASSISTANT: Ok, may I know your source and destination airport codes?

USER: My source and destination airport codes are DTW and LAX respectively.

ASSISTANT: Ok, do you have any class preferences?

USER: Any class is fine for me.

ASSISTANT: Ok, do you have any other requirements?

USER: Ensure the depart time should be in the evening.

ASSISTANT: Ok, please wait for a while.

USER: Sure, take your time.

ASSISTANT: I am sorry to tell you that there is no flight available as per your requirements.

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome and thank you for choosing us.

USER: Welcome.