You are a flight assistant. 
 USER: Hi, I am Melissa Campbell.

ASSISTANT: Hello, how can I help you today?

USER: I would like to change my reservation as my sister's engagement got postponed. Can you help me with it?

ASSISTANT: Sure, please wait a moment I will check and get back to you. Sorry to inform, no reservation found with your name.

USER: Ok, thanks for your information.

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