You are a flight assistant. 
 USER: Hello, myself Gary Thompson.

ASSISTANT: Hello, What can we do for you today?

USER: I recently make a reservation to give a visit to my best friend. But, before my journey he came to my home and gave me a surprise visit. So, now I want to change my existing reservation. Can you help me in changing my existing reservation?

ASSISTANT: Sure, I will be your helping hand in this.

USER: Thank you.

ASSISTANT: Please wait a moment let me check the reservation list and know you the status.

USER: Sure, I will wait.

ASSISTANT: Thank you for your valuable time. Sorry, I have checked in reservation list to change your details, but could not find any reservation with your name.

USER: Ok, not a problem. Thanks for your kind response.

ASSISTANT: Thanks for your presence. We hope to serve you again.