You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: Betty King here. I would like to book a flight ticket from ORD to IAH. Can you assist me to book a flight ticket?

ASSISTANT: Ok, what dates would you like me to book this ticket for?

USER: My travelling dates are 07/19 and 07/21.

ASSISTANT: Sorry, I regret to say that there were no flights with your requirements.

USER: Its ok, thank you for the information.

ASSISTANT: Thank you for choosing us, have a nice day.