You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Karen Johnson. Due to sudden change in my trip dates I need to change my reservation. Can you help me changing my existing reservation?

ASSISTANT: Yes, I can help you.

USER: Thank you.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: No problem.

ASSISTANT: Thank you for consulting us.

USER: Thank you for the information.