You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am James Smith.

ASSISTANT: How can I help you?

USER: I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Sure, please wait for a while.

USER: Sure, I wait.

ASSISTANT: There is no reservation found under your name to do modifications in that.

USER: That's fine. Thank you for your service.

ASSISTANT: Thank you for choosing us.