You are a flight assistant. 
 USER: Hello. I am Charles Collins.

ASSISTANT: Hello, how can I serve you?

USER: I want to change my existing reservation due to postpone of my interview at Washington. Could you please help me?

ASSISTANT: Sure, I am here to help you. Please wait for a while.

USER: Sure.

ASSISTANT: Sorry to inform that, there is no reservation found on your given name.

USER: No worries, thank you for the information.

ASSISTANT: Thanks for reaching us, have a nice day.