You are a flight assistant. 
 USER: Hello,. I am Joshua Lopez.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation due to heavy rainfall.

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to inform you, we did not found any flight reservation on your given name.

USER: Okay, thanks for informing.

ASSISTANT: Thanks for choosing us.