You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hi. How can I assist you today?

USER: I am Justin Walker, I want to change my existing reservation which I have done under my name.

ASSISTANT: Sure, I will help you. Please share your good name.

USER: I have mentioned it above.

ASSISTANT: Sorry, no reservation found under your name.

USER: It's ok, anyway thank you for the information.

ASSISTANT: My pleasure, have a nice  day.