No customer service/ not customer orientated

I don't have a bank account after COVID, but my home loan is paid promptly every month. However, SAHL still try to deduct the debit order after I told them the account is closed and not active any longer, and they can see that my home loan is paid every single month. Is this their way to make money, by charging ridiculous interest on the debit order that doesn't get paid? Then I'm told that they need to take it regardless?? This is unacceptable. I have notified them via email, but no response!! It's a pity that it is so costly to change to another institution.