You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Justin Martin.

ASSISTANT: How may I assist you for the day?

USER: I want to change my existing reservation, can you help me with that?

ASSISTANT: Sure. We are sorry to inform you that, There is no reservation found on Justin Martin.

USER: Ok, no problem.

ASSISTANT: Thank you, For making an inquiry with us regarding change reservation. Have a great day.

USER: Thanks for your response.