You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Barbara Collins.

ASSISTANT: Collins, how can I help you today?

USER: My holiday vacation has been postponed.Can you please help me for changing the existing reservation?

ASSISTANT: Sure, let me check.

USER: Ok.

ASSISTANT: Collins, I have found reservation by your name. May I know your new travel dates?

USER: My travelling dates are 04/03 and 04/05.

ASSISTANT: Can you provide me your airport codes?

USER: My source airport code is ORD and destination airport code is MCO.

ASSISTANT: Please wait for a moment. Thank you for waiting, but there are no flights available to MCO on 04/03.

USER: That's ok, no problem. Thank you for your service.

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

USER: Welcome.