How do I stop ABSA from calling me every day

How do I stop ABSA from calling me every day? ABSA Personal Loans' Collection Department calls me on a daily basis, because the idiots who work there think my payments are behind. They called me again today, shortly after my Debit Orders to pay the study loans went through. When I get angry, because they keep calling me, they throw the phone down. ABSA, you are useless, pathetic, *********** and stupid. And don't tell me it is the system. Someone has to tell the system what to do. So, then it is that person who is ***********, etc. If I receive one more call, SMS or e-mail from ABSA, I will start proceedings against you for harassment. One would be better off at VBS Bank. To think that ABSA was once rated the best bank in SA. This is why; they are more concerned about pleasing their shareholders, incl. the PIC than their clients and focusing only on transformation, rather than appointing competent staff. I can't wait to close my accounts with them.