Mtn ****** me

On the 21st of November I went to pay my account with the amount of R1600 at Bronkhorstspruit MTN. To my surprise the email I got said I paid R1370 and I didn’t not get the confirmation of payment on the same day, I received the email says later. I would like to know what happened and how did it happen. The cashier who assisted me is a lady called Nyiko.