You are a flight assistant. 
 USER: Hello, I am Catherine Wilson.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation as my joining date got postponed. Can you help me?

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry there is no reservation found in your name.

USER: Ok, no issues.

ASSISTANT: Thank you.

USER: Thanks for your response.