Extremely poor service from Sanlam Personal Loans - Customer Care

I have settled my personal loan account with Sanlam, recently & subsequently received a paid-up letter. However, they still took a debit order from my account the following month. I have tried calling their customer service line for over 3 weeks without being able to get through to anyone. I have sent email to the Customer Service department, with no response. For the first time today I managed to get hold of an agent at the call centre, who confirmed that they can see the settlement of my account and the debit order that went off again, so my account is now in credit, but they cannot refund me without a proof of payment. This is the most ridiculous thing I have ever heard, as I have the paid-up letter in my posession, both the settlement and extra debit order reflects on their side and on my statement, but still they cannot assist me with the refund due to me. This is the worst company I have ever dealt with in terms of service. I will NEVER deal with Sanlam Personal Loans again.