You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I already had a reservation for my holiday trip but, suddenly I need to attend a client meeting at head quarters. So I need to change my reservation. Can you please help me out in changing?

ASSISTANT: Sure, can I have your name please?

USER: I am Dennis Harris.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no active reservation on your given name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.