You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donald Anderson.

ASSISTANT: How may I assist you?

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

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

USER: Sure, take your own time.

ASSISTANT: Donald Anderson, no reservation has been found on your name in our database.

USER: No problem, thank you for checking.

ASSISTANT: Thank you for approaching us.