You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my reservation due to postponed of my exam, so please help me.

ASSISTANT: Sure, may I know your name please?

USER: Sure, I am Sarah Walker.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: There is no reservation found with your given name.

USER: No issues, thank you.

ASSISTANT: Thank you for choosing us.