Debit order cancelled but still being debited

I requested a form to cancel my debit order last year in september so i can pay manually, i got the form, signed it and sent it to AFHCO. 7 months later they are still trying to debit that account but it keeps bouncing back because i have changed accounts. I have accumulated charges over R 8000 because of that. I have sent emails, called the head office but to no avail , got no assistance. If i dont pay my rent in protest till they fix it they switch off my electricity and lock me outside.