You are a flight assistant. 
 USER: Hello, I am William Walker.

ASSISTANT: Hello, how can I aid you?

USER: I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, please wait for a second. I will revert to you.

USER: Ok.

ASSISTANT: Thanks for waiting. There is no reservation found against your name.

USER: Ok, no problem.

ASSISTANT: Thank you for approaching us.

USER: Thank you.