Payments Not Being updated and ruining Client's ITC profile

I have had a Sheet Street account for almost a year and have been paying it up to date each month. On the 28th of April 2021, I made a payment R180 when the account instalment due was R175(due on the 1st of May 2021).

On the 13th of May I receive an sms thanking me for my payment but stating that there is still an outstanding amount of R125 and I should call to "avoid arrears". So I called and then got to through to a lady and explained the situation. She told me that she would put me through to the accounts department for them to "update my payment". Why the payment wasn't updated, I don't understand. I held for too long and eventually ran put of airtime.

On the 20th, another similar sms. I ignored it. Today(27th May) I checked my statement and I still have an overdue amount of R125. I called Sheet Street and spoke to Maria who advised that on the system it shows me having made a late payment of R180 and that the statement was issued on the 12th of May before I made a payment. This is of course nonsense. I paid on the 28th of April. She confirmed that the only due amount is R125(due on the 1st of June) and the account is up to date. I paid R180 again as usual.

Then a few minutes later, another sms comes in thanking me for my payment and that my account has an overdue amount. What on Earth is going on at Sheet Street Accounts Department? You are messing with my payment profile on ITC showing late payments when I paid you even before the due date! Fix this and call me!