You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Jack Carter.

ASSISTANT: How may I guide you, Jack?

USER: Due to some personal issues, I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, I will help you. Jack, no reservation has been found on your name in our database.

USER: Ok, that's fine. Thank you for the information.

ASSISTANT: Thank you for choosing our service.