You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Ryan Lopez. Due to an issue in my office, I need to change my existing reservation.

ASSISTANT: Sure, Please wait for a while, I will check and get back to you.

USER: Sure.

ASSISTANT: Sorry to tell that there is no reservation found on your name.

USER: Ok, no problem. Thanks for your service.

ASSISTANT: Thank you for approaching  us.