You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I serve you?

USER: I want to cahnge my existing reservation due to postpone of my meeting so, can you please change my reservation?

ASSISTANT: Sure, let me know your good name please.

USER: My name is Alexander Collins.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Thank you for waiting. Unfortunately we didn't found any reservation by your name.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for reaching us.