You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am David Parker.

ASSISTANT: How can I help you at this moment?

USER:  I want to give a surprise to my brother by attending his convocation day on 04/19, can you please help me in booking a flight ticket?

ASSISTANT: Sure, I will help you with that. Can you please mention your preferable airport code names?

USER: My source is ORD and destination is IAH.

ASSISTANT: Is there any trip that your planning to ORD?

USER: My return date is 04/21.

ASSISTANT: Thank you for providing your travel details. I will put the conversation on hold to check the best flights available in your route.

USER: Sure.

ASSISTANT: Sorry for the inconvenience no flights available in this route as per your requested dates.

USER: No issue, thank you.

ASSISTANT: Thank you for visiting us, have a good day David Parker.