You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Paul King.

ASSISTANT: How can I assist you?

USER: I want to change my existing reservation. Due to my meeting has been postponed, could you please help me to change my reservation?

ASSISTANT: Sure, I will help you with that.

USER: Ok.

ASSISTANT: We didn't find any active reservation under your name in our database.

USER: Not a problem. Thank you very much for your help.

ASSISTANT: Thank you for reaching us.