You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Andrew Carter.

ASSISTANT: How may I guide you?

USER: Can you please help me in changing my existing reservation details?

ASSISTANT: Sure, I will help in changing your ticket.

USER: Thank you.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Based on your request, there is no reservation that is obtained when I check in our previous ticket booking list.

USER: That's ok, thank you for the information.

ASSISTANT: Most welcome.