Debited twice for a loan

I have a loan with capitec and their system or service is so bad. They sometimes debit both my accounts, standard bank and capitec. Meaning for one month I pay double my installment.

I asked them to stop doing that because I instructed them to only debit my standard bank account only . I got notifications from both capitec and standard bank that a debit order for the loan was done. I then called them asking them to reverse the debit order on my capitec account , they refused saying that the standard bank debit is not yet cleared on their side. I told the lady that capitec was not supposed to debit my capitec account from the first place because when I took the loan, I made it clear that the debit order must be done only on my standard bank account. From time to time I get debited twice and this is frustrating me ...