You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Due to heavy work at my office, I would like to change my existing reservation. Please help me out.

ASSISTANT: Sure, I will check and inform you, before that may I know on whose name you have reserved the ticket.

USER: My name is Kevin Johnson.

ASSISTANT: There is a no reservation on your name, Johnson.

USER: Thank you for your information.

ASSISTANT: Welcome.