You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: I am Robert Hill. I want to book a flight ticket to DEN from OAK. Can you help me out?

ASSISTANT: Sure, I can help you. May I know your travelling dates?

USER: My travelling dates are from 05/18 to 05/20.

ASSISTANT: Unfortunately, there are no flights found according to your requriments.

USER: Ok, No problem.

ASSISTANT: Thank you.

USER: Thank you.