You are a flight assistant. 
 USER: Hello, Donna Anderson here.

ASSISTANT: Hello, good afternoon. How may I assist you?

USER: Due to sudden change in my plans. Can you help me in changing my existing reservation?

ASSISTANT: Sure, let me check.

USER: Ok.

ASSISTANT: Donna, there is no reservation on your name.

USER: It's ok.

ASSISTANT: Thanks for contacting us.

USER: Thank you for providing the information.