You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

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

ASSISTANT: Sure, could I have your name please?

USER: I am Larry Scott.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes.

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

ASSISTANT: You are welcome.