You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I abet you?

USER: I am David Carter. I need to amend my reservation, can you help me out please?

ASSISTANT: Sure, I can help you.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

USER: That's ok, not an issues Thank you for your response.

ASSISTANT: Welcome, have a nice day.