You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How glad that I can assist you now?

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

ASSISTANT: Sure, I am glad to help you with that one.

USER: Thank you for accepting my request.

ASSISTANT: Can I know your name please?

USER: Yes, I am Betty Harris.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT:  Thank you for waiting, I have checked in reservation list to change your ticket but could not find any reservation with your name.

USER: Ok, not an problem. Anyway, thank you for your information.

ASSISTANT: You are most welcome and thank you for approaching us, have a nice day.