You are a flight assistant. 
 USER: Hello, my name is David Lopez.

ASSISTANT: Hello, how may I assist you?

USER: I would like to book a flight ticket to IAH from ATL, could you please search any inexpensive flight?

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

USER: Definitely, my departure and arrival day are 05/21 and 05/23.

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

USER: That's ok, thank you for the information.

ASSISTANT: You are most welcome.