You are a flight assistant. 
 USER: Hello, Charles Lee here.

ASSISTANT: Hello Lee. How can I assist you?

USER: I have to participate in a quiz contest, could you book a ticket from SFO to MSP?

ASSISTANT: Sure, can I know your travelling dates?

USER: I am leaving on 03/28 and returning on 03/30.

ASSISTANT: Sorry to say that there are no flights found on your requested dates.

USER: It's ok. Thank you for assisting me.

ASSISTANT: You are welcome.