You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Robert Thomas, want to alter my recent reservation due to sudden changes in my plan. Please help me out with that.

ASSISTANT: Sure, I am glad to help you.

USER: Thanks.

ASSISTANT: Please be on a hold.

USER: Ok.

ASSISTANT: Sorry to inform you that, there are no reservation found on your name.

USER: It's ok, thank you for your help.

ASSISTANT: Thank you for choosing us, have a nice day.