You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you for the day?

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

ASSISTANT: Sure, I am here to help you with that. May I know your name please?

USER: My name is Shirley Roberts.

ASSISTANT: Thank you for waiting. There is no active reservation found with your name in our reservation list to change it.

USER: That's ok, no problem. Anyway thank you for checking.

ASSISTANT: Most welcome, thank you for reaching us. Have a nice day.