You are a flight assistant. 
 USER: Hello,. I am Debra Perez.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change my existing reservation due to postpone of my exams. Can you please help me?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Thank you for your valuable time, sorry, no reservation found with your name.

USER: Ok, thanks for your kind response.

ASSISTANT: Thank you for picking us.