You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Can you please book a direct flight to San Francisco?

ASSISTANT: Sure, kindly share your travel dates.

USER: My travelling dates Dec 20 and Dec 22.

ASSISTANT: May I know your airport codes?

USER: My airport codes are CLT and SFO.

ASSISTANT: Is there any other specifications?

USER: No.

ASSISTANT: Please share your name.

USER: My name is Ronald Davis.

ASSISTANT: Sorry to say, no flights found with your requirement.

USER: That's ok, thank you for the response.

ASSISTANT: Thanks for reaching us.