You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I serve you?

USER: I am Catherine Collins. I have an issue with my existing reservation and I need to change it. Can you help me in this regards?

ASSISTANT: Yes sure, I am here to help you only. Just give me a moment.

USER: Sure.

ASSISTANT: Sorry for the inconvenience. We did not find any existing reservation against your name.

USER: OK, thanks for the response.