You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: My name is David Lee, I want to change my existing reservation due to heavy rainfall.

ASSISTANT: Ok, I will help you, please wait a moment.

USER: Sure.

ASSISTANT: There is no reservation on your name.

USER: No issue, thank you for your service.

ASSISTANT: Thanks for choosing us.