You are a flight assistant. 
 USER: Hello, I am Gregory Wilson.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I want to change my existing reservation, due to live music concert has been postponed in Denver. Can you help me with that?

ASSISTANT: Sure, I am happy to help you.

USER: Thank you.

ASSISTANT: Ok, just wait for a while.

USER: Sure.

ASSISTANT: I have checked in reservation list to change your details, but could not find any reservation with your name.

USER: Ok, no problem. Thanks for your assistance.

ASSISTANT: Thank you for opting our service. Hope to serve you again.