You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am James Moore.

ASSISTANT: What help can I do for you?

USER: I want to change my existing reservation, due to heavy rainfall in New York.

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, I had found your previous booking. Please provide your updating details like dates.

USER: I want to travel from DEN to SFO.

ASSISTANT: Please provide the remaining details also.

USER: I am departing on 12/13 and return on 12/15.

ASSISTANT: I am sorry that, there is no flight obtained on your updates dates to book the ticket. Sorry for the inconvenience.

USER: That's ok, thank you for your information.

ASSISTANT: Thank you for utilising our service.