You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Charles Young.

ASSISTANT: What help do you want from our travel agency?

USER: I want to change my existing reservation, can you help me in booking?

ASSISTANT: Sure, I am happy to help you in modifying the ticket details once I have found your ticket.

USER: Thank you.

ASSISTANT: Ok, please give me a moment.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry to inform you, there is no reservation found with your name in our database.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: My pleasure. Thank you for choosing us.