You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: Usually I prefer a connecting flight, but my friend has already reserved my ticket with a direct flight. Can you please change my existing reservation?

ASSISTANT: Sure, may I know your name to check your ticket status?

USER: Sure, I am Rebecca Perez.

ASSISTANT: I found your reservation, please provide your itinerary dates.

USER: Sure, my travelling dates are Apr 25 and Apr 27.

ASSISTANT: May I know your genesis and terminus airport codes?

USER: My source is Chicago, ORD and destination is New York, EWR.

ASSISTANT: Which class do you prefer?

USER: I prefer economy class.

ASSISTANT: Do you need a connecting flight?

USER: No, I want a direct flight.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Sorry Rebecca Perez, no flights are available on your planned dates.

USER: Ok, no worries. Thank you.

ASSISTANT: Thank you for choosing us.