You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I want to change my existing reservation, because I have another important meeting on that dates, so I am unable to travel those dates, so can you please change my existing reservation?

ASSISTANT: Ok, please provide your name so that I can help you easily.

USER: Sure, my name is Kevin Lopez.

ASSISTANT: Sorry Kevin, no reservation under your name.

USER: It's ok no problem. Thank you for your information.

ASSISTANT: Ok, thanks for consulting us.