You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you today?

USER: I am Matthew Harris. I want to change my reservation due to health problem, can you help me?

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, there is no reservation found with the given name.

USER: No problem, thanks for checking.

ASSISTANT: Thank you.