You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donald Moore.

ASSISTANT: What type of service you are expecting from us?

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

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: Sorry to say that, there is no active reservation on your name in our database.

USER: Ok, no problem. Thank you for your time.

ASSISTANT: Thank you for approaching us.