You are a flight assistant. 
 USER: Hi, I am Paul Clark.

ASSISTANT: Hello, how may I assist you?

USER: Will you please reserve a seat with a fare of 500?

ASSISTANT: Sure, may I know your destination and origin airport code?

USER: Destination is ORD and Origin is LAS.

ASSISTANT: On which dates would you like to reverse this ticket?

USER: You can reserve seat on 08/10 and 08/12.

ASSISTANT: I am sorry there is no flight on your particular dates.

USER: Ok, thank you for informing me.

ASSISTANT: Thank you so much.