You are a flight assistant. 
 USER: Hello, Ronald Smith here.

ASSISTANT: Hello, how can I help you now?

USER: Can you please book me a ticket from DFW to DEN?

ASSISTANT: Can you please mention the travelling dates of your journey?

USER: My travelling dates are from 08/22 to 08/24.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry Ronald, there are no flights found on your requirement.

USER: It's ok. Thank you for providing information.

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