You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you today?

USER: I am Mary Campbell, can you help me for changing existing reservation?

ASSISTANT: Sure, I will help you. Please hold on a moment to check your previous reservation status.

USER: Ok, I will wait for your response.

ASSISTANT: We regret that, there is no reservation found with your name in our records.

USER: Oh! it is ok, no problem. Thank you for your services.

ASSISTANT: Thank you for approaching us, have a great day.