You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I have an appointment with doctor on the dates of journey. So, I would like to change my existing reservation.

ASSISTANT: Can you please share your name to find whether your reservation is existed or not?

USER: My name is Christine Baker.

ASSISTANT: Sorry, there is no reservation found under your name. Thank you for reaching us.

USER: Ok, that's fine. Thank you for the information.

ASSISTANT: You are welcome.