You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, may I know how best I can help you today?

USER: I am Dennis Miller. I am planning to travel from ORD to DCA, can you help in booking a flight?

ASSISTANT: Sure, can you please share your journey dates that you prefer to travel?

USER: My travelling dates are 04/20 to 04/22.

ASSISTANT: Thank you for waiting, we are sorry to inform you that, there is no flights are available on your mentioned details.

USER: That's ok, thank you.

ASSISTANT: Your welcome, have a nice day.