You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I would like to change my reservation due to post pone of my sister's engagement. Please help me with it.

ASSISTANT: Sure, kindly mention your name?

USER: Reservation was done by the name Melissa Brown.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say, no reservation found with your name.

USER: Fine, thanks for your information.

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