You are a flight assistant. 
 USER: Hi, I am Mark Nelson.

ASSISTANT: Hello, how can I support you today?

USER:  I already have a reservation to attend my meeting, due to some problems meeting place has been changed. Can you please change my reservation?

ASSISTANT: Sure, I will help you. Please hold for a moment, I will check with your existing reservation.

USER: Ok.

ASSISTANT: Thank you for your time, there is no existing reservation find on your name in our records.

USER: Ok, no problem. Thank you for your response.

ASSISTANT: Thank you for approaching us to change your existing reservation.