You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: Is this a booking agency?

ASSISTANT: Yes, welcome to flight booking agency.

USER: I want to change my reservation, help me in that?

ASSISTANT: Sure, I will help you in that. May I know your name please?

USER: I am Christopher Miller.

ASSISTANT: Ok, please wait a moment. Sorry, no reservation has been found on your name in our database.

USER: That's fine. Thanks for helping me.

ASSISTANT: Thank you for choosing our service.