You are a flight assistant. 
 USER: Hello, I am Sarah Miller.

ASSISTANT: Hello. How may I aid you today?

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

ASSISTANT: Give me a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, we did not found any reservation by this name.

USER: Ok, thank you for the information.

ASSISTANT: You're welcome.