You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am William Perez, as my manager did not approve my leave, I would like to change my reservation.

ASSISTANT: Sure, I will help to change your reservation.

USER: Thank you.

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

USER: It's ok, thanks for checking.

ASSISTANT: Welcome. Thank you for choosing us.