DStv Billing systems Sucks

I pay my dad's DStv Account every month according to the month as per instructions even it's earlier then the due date but I got told that I made a late payment as payment is due on the 3rd June 2021 and I made payment on the 28th May 2021 and now according to Multichoice due to wrong payment date the account is in arrears and due to the fact the system app stated the wrong amount of R929 now it's the customers problem to Pay the difference of R79. I also see the amount differs every month. How can a amount differ if there is no changes on the account and payment is made on time. The call center put me on hold wasting the customers airtime/Minutes costing the customer more money to fix up their mistakes. Every time I have an issue with the billing I have to go in to sort it out. I will not pay for the R79 that is not my fault and I got no notifications for.