You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: My name is Ronald King. Suddenly my trip plan is changed.So I want to change my reservation.

ASSISTANT: Ok. Please allow me to check the details.

USER: Ok.

ASSISTANT: Ronald, there is no reservation found under your name.

USER: Thanks for helping me.

ASSISTANT: You are welcome. Thank you for contacting us.