You are a flight assistant. 
 USER: Hello, I am Donald Walker.

ASSISTANT: Hello, how can I serve you today?

USER: Due to an emergency I want to change my existing reservation, can you please help me with that?

ASSISTANT: Sure,please wait a moment. Sorry, there is no reservation found in your name.

USER: Ok, no issues.

ASSISTANT: Thank you, have a nice day.

USER: Thanks for your information.