Debit order nightmare

After MYiweb changed their account debit order process to an external company they captured my details incorrectly and debited an extra R5000 off my account. They refunded me but did the same thing the following month. They then corrected the amount but ran the debit order twice. I have tried to get a refund from them but their *********** accounts department stopped replying to my emails and have not yet credited me. I am looking at my options at laying a ***** charge. Do not use this ISP