You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I oblige you today?

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

ASSISTANT: Sure, please share your good name?

USER: Sure, my name is Donald Lopez.

ASSISTANT: Please hold a moment.

USER: Sure, I will wait for your reply.

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

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

ASSISTANT: Thank you.