You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Rebecca Thomas.

ASSISTANT: How can I aid you?

USER: Please book me a ticket from IAH to ORD to meet my family.

ASSISTANT: Sure, I can help you with that. May I know your planned travel dates please?

USER: I have planned to on May-18th and May-20th.

ASSISTANT: Ok, can you please let me know your class preference?

USER: I am flexible any class.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Sorry to inform you that there are no flights available for you on those dates.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for choosing us.

USER: Thank you.