You are a flight assistant. 
 USER: Hello. I am Sarah Lopez.

ASSISTANT: Hello, how may I aid you?

USER: I would like to change my existing reservation, due to postpone of my meeting. Can you please help me in changing?

ASSISTANT: Sure, please be on hold.

USER: Ok.

ASSISTANT: Thank you for your time. Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for reaching us.