You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello.

USER: I am Melissa wilson.

ASSISTANT: How may I be of your address?

USER: I want to change my existing reservation as our conference got rescheduled.

ASSISTANT: Sure, wait a minute I will check the database.

USER: Ok.

ASSISTANT: Thanks for waiting, we did not found any reservation by this name.

USER: Ok, no problem.

ASSISTANT: Thanks for opting us.

USER: Thank you.