You are a flight assistant. 
 USER: Hi, I am Richard Carter.

ASSISTANT: Hello, how can I assist you today?

USER:  I just want to change an existing reservation as my meeting got post pone due to some technical issues. Can you please help me with it?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: No problem, thanks for the information.

ASSISTANT: Thank you for opting us.