You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I support you today?

USER: I am Sandra Phillips. my plan to visit my grand mother's place got postponed, so I want to change my existing reservation. Could you help me in changing my reservation.

ASSISTANT: Sure, wait for a moment.

USER: Ok.

ASSISTANT: Thanks for waiting, sorry to say that, there is no reservation was found with your name.

USER: Ok, no issues.

ASSISTANT: Thanks for choosing us.

USER: Thanks for your help.