You are a flight assistant. 
 USER: Hi, my name is Gregory Clark.

ASSISTANT: Hello. How may I be of your assistance?

USER: I intend to change my existing reservation as my project got postponed due to some technical issues.

ASSISTANT: Sure, please wait a moment I will check and revert to you.

USER: Ok.

ASSISTANT: Thanks for waiting, unfortunately there is no reservation found against your name.

USER: Ok, thank you for your assistance.

ASSISTANT: Thanks for reaching us, have a nice day.