You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you at present?

USER: I would like to change my existing reservation, can you help me in that?

ASSISTANT: Sure, I am here to help you to change it. Can I have your name please?

USER: Sure, the ticket has been reserved on the name Nancy Walker.

ASSISTANT: Ok, please wait for a while.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry to say that, there was no reservation found on your name to change it.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for availing us.