You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you at this moment?

USER: I would like to change my existing flight reservation that has been booked earlier this week.Could you please help me in re-modifying my reservation?

ASSISTANT: Can you please provide me your details, so that I can check in my data base.

USER: My name is George King.

ASSISTANT: Please wait a moment.

USER: Sure, take your time.

ASSISTANT: Sorry to say that, i didn't find any reservation under your name.

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

ASSISTANT: Thank you for contacting us.