You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I am Gregory Hall. I want to book a flight ticket from DCA to HOU, can you help me with that?

ASSISTANT: Sure, Gregory Hall, we are gleeful to serve you. Could you please ensure your journey dates?

USER: My journey dates are from 09/13 to 09/15.

ASSISTANT: Ok, please hold on for a while.

USER: Ok.

ASSISTANT: Thanks for your valuable time. Sorry, no flights were found based on your schedule.

USER: Ok, no problem. Thanks for your service.

ASSISTANT: Have a pleasant day.