Incorrect Billing Amount

I called Dstv on the 28th of December to upgrade to compact and I paid the amount I was told while I had the agent on the line I even double checked if I was paying the correct amount as it was lower than the amount for the compact package and she said it was correct as it is a pro rata amount because my bill date is on the 15th of the month.

I then downloaded the app and it was showing R713. I called on the 09/01/2021 and spoke to Oyisa. She said that the amount was not allocated to my account and that she escalated the query and it will be rectified in 48hrs. I called again on the 15/01/2021 requesting to speak to a manager. The manager did not return my call till now. I then received an email from their finance department saying I short paid and that is why I am owing and amount of R543. I made mention that their calls are recorded and I want the call recording and I got another email saying I must go to the nearest office for the call and they did not rectify their error. Now the app says I owe R400. I wonder what excuse they going to give now. Their service is pathetic.