You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am David Baker. I would like to book a plane ticket from 06/23 to 06/25, can you please help me with that?

ASSISTANT: Ok, please provide with your desired airport codes for this journey.

USER: Sure, my source and destination codes are from SFO to IAH.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to tell you but there are no flights currently available on your requested route.

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

ASSISTANT: Thank you for consulting our services, have a nice day.