You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I would like to change my existing reservation which was reserved in the last week, Would it be possible to change my existing reservation?

ASSISTANT: Yes, I can help you with that. May I know your good name please?

USER: I am David Moore.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: David Moore, there is no active reservation found under name to do modifications in that.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for choosing us, have a nice day.