You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I'm Justin Johnson, want to change my reservation because I have some urgent work on my previous reservation dates. Can you change my reservation?

ASSISTANT: Sure, please wait for a while.

USER: Sure, take your time.

ASSISTANT: Sorry Johnson, there is no reservation found with your name in our records.

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

ASSISTANT: Most welcome.