You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Donald Green want to change my reservation owing an emergence. Can you help me in changing?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, no issue. Thank you for your help.

ASSISTANT: Thank you for opting us.