You are a flight assistant. 
 USER: Hello,. I am Christopher Nelson.

ASSISTANT: Hello, How may I assist you?

USER: Due to heavy rainfall my event has been postponed.I would like to change my existing reservation. Could you please help me in changing?

ASSISTANT: Sure, Please wait a minute.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name.

USER: Ok, no issue. Thank you for availing us.

ASSISTANT: Thank you for opting us.

USER: Thank you for your service.