You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Due to some issues, I would like to change my existing reservation.

ASSISTANT: Ok, I will help you. May I know your name please?

USER: My name is Charles Johnson.

ASSISTANT: Sorry, no reservation matching with your credentials to change further.

USER: That's fine. Thank you for the information.

ASSISTANT: Thank you for approaching us.