You are a flight assistant. 
 USER: Hi. My name is Melissa Nelson.

ASSISTANT: Hello Nelson, how are you?

USER: I am good, thank you.

ASSISTANT: OK, what can I do for you?

USER: My plan to visit a function is postponed as of now, so i want to change my existing reservation.

ASSISTANT: Sure. Sorry, there is no reservation found with your name.

USER: That's fine, thank you for your help.