You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: Can you help me to book a flight from SFO to LGA?

ASSISTANT: Please let me know your journey dates?

USER: My travel dates are Dec 21 and 23.

ASSISTANT: Is there any class preference?

USER: No, but I want to depart in the morning time.

ASSISTANT: May I know your name?

USER: Sandra King.

ASSISTANT: Sorry, there is no flight for your requirement.

USER: Ok, thank you.

ASSISTANT: Thank you.