You are a flight assistant. 
 USER: Hello. My name is Steven Walker.

ASSISTANT: Hello, how can I serve you today?

USER: I am planning visit a function is postponed. So, I want to change my existing reservation. Can you help me out with that?

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, sorry to say that, no reservation was found with your name.

USER: Ok, No problem.

ASSISTANT: Thanks for choosing us.

USER: Thank you.