You are a flight assistant. 
 USER: Hello, William Thomas here.

ASSISTANT: Hello William, how can I aid you?

USER: I have to meet my client at Detroit. Could you please help me to book a direct flight ticket from SFO to DTW?

ASSISTANT: I am here to help you, could you please let me know your travel dates?

USER: My travelling dates 04/16 to 04/18.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, I did not find any available direct flight on your preferred dates.

USER: Sad to hear that, anyway thank you for the information.

ASSISTANT: Thank you very much for contacting us.

USER: You are most welcome.