You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I am very happy to change my existing reservation because my examination was postponed, now I have much time to prepare for the exam.So please help me in modifying my recent reservation. Can you help me to change my reservation?

ASSISTANT: Sure, may I know your name to check for the previous reservation in our data base?

USER: I am Raymond Hill.

ASSISTANT: Please allow me a moment to check for the previous reservation.

USER: Sure.

ASSISTANT: Your patience is greatly appreciated. Raymond, there is no reservation found under your name.

USER: It's not a problem. Thanks for your valuable information.

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