You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I assist you at this moment?

USER: I am Mark white. I want to change my existing reservation due to sudden occasion at my home. Can you be my helping hand in changing my reservation?

ASSISTANT: Ok, I can search for you and I will help you out.

USER: Sure.

ASSISTANT: Sorry, no reservation found on your name.

USER: Ok, no issues.

ASSISTANT: Thank you for contacting us.

USER: Thank you for your quick response.