You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, we are here to help you. Can I know your name please?

USER: Thank you. Sure, my name is Kevin Miller.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: Ok, no problem. Thank you for your service.

ASSISTANT: Thanks for reaching us, have a nice day.