Bad customer service

I have a STD access loan and I was in arrears and it was handed over to Kwanda and I then asked the arrears amount and was given R1601.92 and I paid it on the 20 March and i sent the POP but I still get calls and messages that I'm in arrears with the same amount. I've tried reaching out to them but they don't respond or if they do they tell me to pay. I'm fed up with them because what they are doing is to **** people.