You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you now?

USER: I am Dennis and I just want to change an existing reservation due to my plan to meet my girlfriend got post pone. Can you help me in change an existing reservation?

ASSISTANT: Sure, I am here to help you. May I now your full name to check reservation?

USER: I am Dennis Williams.

ASSISTANT: Thanks for providing your name, please wait a moment.

USER: Ok.

ASSISTANT: Sorry there is no reservation found don your name.

USER: Ok, no problem.

ASSISTANT: Thanks for contacting us.

USER: Thank you.

ASSISTANT: Have a nice day.