Refund/recall

My old mutual “savings account” went on a negative amount of R10300 for an online purchase I didn’t make,I called their call centre to request they reverse/stop this transaction,my account was then closed but the transaction still went through,the bank had me filling out dispute forms to refund my account and today I’m told there’s nothing they can do as this is an ongoing transaction which I did not authorise and that there’s nothing they can help me with,I’m furious as this is almost my entire salary and they telling me they can’t assist me