You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Sure, may I know your name please?

USER: Sure, myself Stephanie Perez.

ASSISTANT: I am sorry no reservation found on your name.

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

ASSISTANT: Thank you for choosing us.