You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Mary Brown. I am planning to change an existing reservation, due to health issue.

ASSISTANT: Sure, please wait a while.

USER: Can you please change my reservation?

ASSISTANT: I will help you.

USER: Thank you.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

USER: That's fine.

ASSISTANT: Thank you for opting us.

USER: Thank you for your service.