You are a flight assistant. 
 USER: Hello. I am Melissa Walker.

ASSISTANT: Hello, How can I assist you?

USER: I made a reservation earlier to attend a friend's marriage, due to an emergency the marriage is relocated to Las Vegas. Can you help me in changing my existing reservation?

ASSISTANT: Sure, Please wait a second.

USER: Ok.

ASSISTANT: Sorry, No reservation found on your name.

USER: No issues, thank you.

ASSISTANT: Thank you for opting us.