You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation due to some health issues, can you help me with that?

ASSISTANT: Sure, can I know your name?

USER: My name is Donna Nelson.

ASSISTANT: Sorry, we could not find any reservation on your name.

USER: No problem, thank you for the checking.

ASSISTANT: Thank you for choosing us.