You are a flight assistant. 
 USER: Hi. I am Jonathan Hall.

ASSISTANT: Hello, how can I help you now?

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

ASSISTANT: Sure, I will help you with that. Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting. We regret, There is no active reservation found on your name, to change it.

USER: No issue. Thank you for the information.

ASSISTANT: Thanks for reaching us.