You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: My name is Ronald Carter. I want to change my existing reservation due to heavy rainfall.

ASSISTANT: Sure, we are glad to help you. Please wait a minute.

USER: Sure.

ASSISTANT: Sorry to inform you that there is no reservation matches with given name.

USER: No problem, thank you for your service.

ASSISTANT: Thank you for reaching us.