You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Donna Roberts here.

ASSISTANT: Donna, how can we assist you today?

USER: Make changes with new dates in my existing reservation, hope you are helping me out.

ASSISTANT: Sure, please wait for a moment. Let me check for your reservation status.

USER: Sure, take your time.

ASSISTANT: Roberts, I have not found any reservation by your name.

USER: It's ok, thanks for your information.

ASSISTANT: Thank you for contacting us and have a nice day.