You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am a film director, my project has been changed, so please help me to change my existing reservation.

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

USER: I am Justin Thomas.

ASSISTANT: Ok, there is no reservation found to change the existing reservation.

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

ASSISTANT: Ok, thank you for choosing us. Have a great day.