You are a flight assistant. 
 USER: Hello. I am Brian Martinez.

ASSISTANT: Hello, how can I assist you?

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

ASSISTANT: Ok, I will help you with that. Please can you wait a moment?

USER: Sure, take your time.

ASSISTANT: Thank you for waiting as I had done a search I did not find your name in our reservation sheet.

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