You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change my existing reservation, due to health issues. Can you please help me?

ASSISTANT: Sure, may I know your name for the changing process?

USER: My name is Margaret Roberts.

ASSISTANT: Sorry, we couldn't find a reservation on your name to change.

USER: No problem, thank you for your information.

ASSISTANT: Welcome, thank you  for reaching us.