You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: Sure, I am glad to help you.

USER: Thank you.

ASSISTANT: May I know your name?

USER: My name is Jason Perez.

ASSISTANT: Sorry, there are no reservation found on your name.

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

ASSISTANT: Thank you for choosing us.