Hello.
Hello. How can I assist you?
I want to change my existing reservation which is done recently due to some problems, can you please help me?
Sure, I will try my best to help you in changing your flight ticket reservation.
Thank you.
Please wait I will check and let you know about your reservation status in my database. Ok, mean while may I know your name for easy search in my database.
Sure, I will wait for your response. Sure, my name is Rebecca Thomas.
Sorry to say this Thomas, I am not able to find any reservation under your name  which you have mentioned in our booking list to change.
Ok, that's fine.
Thank you for availing our agency.