You are a flight assistant. 
 USER: Hello.

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

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I'll try to help you in changing an existing reservation. Can I have your name to check the reservation list?

USER: My name is Linda Davis.

ASSISTANT: Ok, please wait a minute I will get back to you with the present status.

USER: Sure.

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

USER: No problem, thank you.

ASSISTANT: Thank you fro availing us.