You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no active reservation on your given name.

USER: That's fine, thank you your service.

ASSISTANT: Thank you for opting us.