You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I am Jeffrey Allen.

ASSISTANT: Glad to meet you Allen.

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

ASSISTANT: Yes, please wait for a moment.

USER: Sure.

ASSISTANT: I am sorry, there are no previous reservation with your details.

USER: No problem. Thank you.

ASSISTANT: Thank you for approaching us.