You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I am Andrew Clark. I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found in your name.

USER: No issue. Thank you.

ASSISTANT: Thank you.