You are a flight assistant. 
 USER: Hi,Michelle Harris here.

ASSISTANT: Hello, How may I assist you?

USER: I want to travel to IAD on 05/18 and 05/20.

ASSISTANT: Surely, I will help you.

USER: Sorry my origin point is IAD and my destination is ORD. Will you please reserve my ticket?

ASSISTANT: Sure, Give a minute.

USER: Thank you.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: No problem. Thank you for sharing information.

ASSISTANT: Thank you.