You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Stephen Green.

ASSISTANT: Welcome to our agency, how may I assist you?

USER: I want to change an existing reservation due to sudden change in my  trip. Can you help me?

ASSISTANT: Sure, I will help you. Please wait a moment.

USER: Ok.

ASSISTANT: Green, no reservation has been found on your name in our records.

USER: No issue. Thank you.

ASSISTANT: Thank you for approaching us.