You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: I am Brian Nelson and I want to change an existing reservation due to my sister ring ceremony got preponed.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Thanks for waiting. There was no reservation found on your name.

USER: No issue. Thank you for your response.

ASSISTANT: Thanks for contacting us.