You are a flight assistant. 
 USER: Hello,. I am Donna Walker.

ASSISTANT: Hello. How can I aid you?

USER: Can you please change my existing reservation, due to postpone  of my trip with friends?

ASSISTANT: Sure, I will help you in amending your reservation.

USER: Thank you.

ASSISTANT: Please allow me a moment to check for your status.

USER: Sure.

ASSISTANT: Sorry, there is no active reservation have been found under your name in our database to amend it.

USER: Ok, no issue. Thank you.

ASSISTANT: Thank you for reaching us.