You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT:  To proceed further, can I have your name please?

USER: My name is Stephen Mitchell.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Thanks for waiting, I have gone through the reservation list twice but could not find any reservation active under your name.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome Stephen Mitchell.