You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I already book a flight to Las Vegas to spend my holidays, now I want to change my reservation to new dates. Can you help me to change my reservation?

ASSISTANT: Sure, may I know your name please?

USER: My name is Brandon Taylor.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for opting us.