You are a flight assistant. 
 USER: Hello. I would like change my reservation, can you me in changing the reservation? Donald Walker here.

ASSISTANT: Hi there. Thank you for choosing us to help you today. Yes, of couse I can help you with that. Just give me a moment till I get you details from our system.

USER: Ok.

ASSISTANT: Mr. Walker, it seems there is no reservation done under your name in the system.

USER: That's ok. Thank you for helping me.

ASSISTANT: No problem. Hope you have a good day ahead.