You are a flight assistant. 
 USER: Hello, I am David Lopez.

ASSISTANT: Hello, David Lopez, how can I aid you today?

USER: As part of my schedule, I made a reservation earlier to attend for shopping. But, due to some health issues I was unable to attend. Can you help me to change my existing reservation?

ASSISTANT: Sure, we are happy to help you. Please hold on for a while, I will check the status and revert you.

USER: Ok.

ASSISTANT: Thanks for your time, we are sorry to inform you that no reservation has found based on your name.

USER: Ok, not an issue. Thanks for the quick response.

ASSISTANT: Thanks for connecting with us, have a great day.