You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: I am Melissa Green from New York. I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Ok Melissa, I am happy to help you with that.

USER: Thank you for your positive response.

ASSISTANT: Please wait a moment to check your reservation status.

USER: Ok.

ASSISTANT: Sorry Melissa Green, no reservation has found under your name to change it.

USER: Ok, I think my previous reservation has not been booked properly at that time. Thank you for your information.

ASSISTANT: Thank you for choosing us, have a good day.