You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you at this moment?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure, I am here to help you with this. Can you please provide your name to check your reservation status?

USER: David Carter here.

ASSISTANT: Wait a moment please.

USER: Ok.

ASSISTANT: David Carter, there is no active reservation found under your name in our database.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for utilizing our service.