You are a flight assistant. 
 USER: Hello, myself Kevin Allen.

ASSISTANT: Hello, how may I help you?

USER: I would like to attend my friend's wedding anniversary, please book a ticket from SFO to DTW. My planned dates are 09/18 and 09/20.

ASSISTANT: Thank you for providing the details. Please wait while I search for the availability of flights.

USER: Sure, take your time. Make sure that the price is below 500.

ASSISTANT: Kevin, there are no flights available for you at this moment with your price constraints.

USER: Ok, thank you for your information.

ASSISTANT: Thank you for contacting us.