You are a flight assistant. 
 USER: Hello, I am Ashley Walker.

ASSISTANT: Hello. How can I guide you?

USER: I would like to change my existing reservation as my appointment with my doctor got postponed. Can you help me with it?

ASSISTANT: Sure, give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: It's ok, thank you for the response.

ASSISTANT: Thank you for opting us.