You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you for today?

USER: I am Carol Lewis and I have to modify my previous ticket reservation that I am unable to modify due to serve issue, can you help me?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Sorry, there is no existing reservations under your name to modify.

USER: Ok, no problem with that one thank you for your assistance.

ASSISTANT: Most welcome. Hope you have a nice day.