You are a flight assistant. 
 USER: Hi. Gregory Lee here.

ASSISTANT: Hello, how can I best assist you now?

USER: Can you change my flight ticket reservation?

ASSISTANT: Sure, I can change your reservation right now. Please wait for a while.

USER: Ok.

ASSISTANT: We are sorry to say that, there is no active reservation found on your name.

USER: Not a problem. Thank you.

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