You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Sure, help me with your travel dates.

USER: Thank you. Apr 23th and 25th are my trip dates.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Do you have any other preferences?

USER: I want to return in the afternoon.

ASSISTANT: Please help me with the airport codes.

USER: ATL and IAH are my exact airport codes.

ASSISTANT: May I know your name?

USER: I am Laura Nelson.

ASSISTANT: Sorry, we did not find any flights for you.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for reaching us.