You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, can you share your name please?

USER: Karen Roberts here.

ASSISTANT: Sorry, no reservation found on your given name.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for contacting us.