Pay on Truworths Website - if you want their systems to lose your money

Truworths have been paid, on-time, every time since account opening in 2004. I never really use the account and paid the last instalment on 27 September 2021. Suddenly I'm getting threatening SMSs, my payment profile on ITC is updated to 30 days in arrears and they're phoning me for collection of arrears. I PAID USING THEIR OWN WEBSITE, GOT AN SMS IMMEDIATELY TO THANK ME and now their systems didn't process the payment and I'm the one suddenly in arrears. Their team leaders has attempted to be helpful but I'm still getting collection attempts. IT'S LITERALLY YOUR SYSTEM ERROR. FIX IT. AND DON'T PHONE ME AGAIN. Close the account while you're at it.