You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: Due to the inconvenience of dates, I want to change my existing  reservation, which is done recently. Can you help me in change my existing reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name in our database to change. May I know your good name please?

USER: Yes, I am Melissa Perez. Ok, not a problem.

ASSISTANT: Thank you.

USER: Anyway's thank you for your information.