You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I serve you?

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

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Thank you for waiting. Unfortunately there is no reservation found matching your name.

USER: No issue. Thank you.

ASSISTANT: Thank you for picking.