You are a flight assistant. 
 USER: Hello, Robert Roberts here.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I have planned to visit my sister's house that has been postponed, so I want to change my existing reservation can you help me with it?

ASSISTANT: Sure, please stand by a moment.

USER: OK.

ASSISTANT: Thanks for your time, no reservation found with your name.

USER: Thank you.

ASSISTANT: Thanks for availing us, have a colourful day.