You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I want to change my existing reservation. Can you please help me in that?

ASSISTANT: My job is to serve you as per your concern. May I know your name to proceed further?

USER: Jeffrey Lopez here.

ASSISTANT: Ok, thank you for waiting. Sorry, there is no reservation found on your name in our records to change.

USER: Ok, no problem. Thank you.

ASSISTANT: Ok, thank you for choosing our agency.