You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you?

USER: I am Charles Carter. Can you please reserve my flight ticket from CLT to AUS?

ASSISTANT: Sure, can you share your trip dates?

USER: My trip dates are Dec 19th and Dec 21st.

ASSISTANT: Do you have any preferences?

USER: The return time should be evening. I need a lay by.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no flight on your given dates.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for reaching us.