You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation due to some health problem. Can you help in the changing the flight ticket?

ASSISTANT: Sure, may I know your name for checking?

USER: Sure, I am Robert Perez here.

ASSISTANT: Give me a minute.

USER: Sure.

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

USER: Ok, not a problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.