You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Charles Roberts here.

ASSISTANT: How can I help you Charles?

USER: Could you help me to amend my existing reservation?

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

USER: Ok.

ASSISTANT: Sorry Charles, no active reservation found by your name in our website.

USER: No problem, thank you.

ASSISTANT: My pleasure.