You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: Unfortunately, I would like to change my existing reservation, can you please help me in this condition?

ASSISTANT: Sure, may I know your name?

USER: Ok, my name is Ryan Miller.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: That's fine.

ASSISTANT: Thank you for opting us.

USER: Thank you for your service.