You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I am looking to book a flight ticket from CLT to SFO. Can you help me for that?

ASSISTANT: Sure, I am here to help you. May I know your travel dates please?

USER: My travelling dates are Aug 13 and Aug 15.

ASSISTANT: Ok, do you have any specifications?

USER: My depart time is afternoon.

ASSISTANT: Ok, hold on for a moment. Let me check the best available flight for you.

USER: Sure, I will wait for your response.

ASSISTANT: May I know your name please?

USER: My name is Matthew Green.

ASSISTANT: Sorry, Matthew Green, there are no flights available on your requested dates.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome, thank you for choosing us. Have a safe day.