You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I be of your help?

USER: I need to change my existing reservation, can you please help me?

ASSISTANT: Sure, I'll try to help you in changing an existing reservation.

USER: Ok.

ASSISTANT: Please let me know your name to check the reservation list.

USER: Myself Jacob Walker.

ASSISTANT: Ok, give me some time.

USER: Sure, please take your time.

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

USER: That's ok, thank you for searching my details.

ASSISTANT: Thank you for approaching us.