Capfin refuse to refund after account was settled and did not cancel debit order

I did settled my account. It is paid in full. Capfin confirmed that my account was paid in full via sms and customer care and they stil deducted my debit order from my bank after the account was paid off. I did call Capfin and requested a refund for the amount of R3444 which they debited me unlawfully as the account was paid in full. This morning I received a phone call and they want a proof of payment. They already have all proof and they don't want to refund me.