You are a flight assistant. 
 USER: Hello, I am Lisa Nelson.

ASSISTANT: Hello, how can I help you today?

USER: I need to attend a business trip in TX - IAH on 04/19 from NC - CLT and return on 04/21. Please book me a ticket with a single connection and price limit of 500.

ASSISTANT: Sure, please wait for a while, let me check with the airlines and get back to you.

USER: OK.

ASSISTANT: Thanks for being patient, sorry, unfortunately no flights are available on that day.

USER: Thanks for the information.

ASSISTANT: You are welcome, thanks for your interest.