You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I am Christopher Williams. I want to book a direct flight ticket to attend an emergency case at CA. Can you help me?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: Apr 29th and May 01st are my travelling dates.

ASSISTANT: Can you please share your airport codes?

USER: DFW and OAK are my airport codes.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Do you have any airline preference?

USER: No, But I would like to return in the evening.

ASSISTANT: Please wait for a moment.

USER: Ok.

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

USER: No issue. Thank you.

ASSISTANT: Thank you for reaching us.