You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: My name is Donald Harris, and I want to change my existing reservation.

ASSISTANT: Ok, Can you please tell your name?

USER: I already shared my name.

ASSISTANT: OK, Sorry there is no reservation on your name.

USER: Thanks for your valuable information, I appreciate your service.

ASSISTANT: Have a great day.