You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: Can you help me to change my existing reservation as my exams got postponed?

ASSISTANT: Sure, I'll try to help you in changing an existing reservation.

USER: Thank you.

ASSISTANT: Please let me know your name to check the reservation list.

USER: Myself Margaret Davis.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Thank you for waiting, I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, no problem.

ASSISTANT: Thank you for availing us.

USER: Thank you for checking.