Telkom Bullying Customers

We took out an online LTE Router deal. We were called back by a Telkom salesperson, telling us that they can do a cheaper deal for us with the same router. She mentioned the cooling-off period that applies and we can change the deal (this is mandatory by the way). Three / four weeks later they delivered the product, only for it to be the wrong product (just some other deal online - silly sales girl did a down-sale). So now, two months later, they are debiting the bank account and still haven't cancelled the deal or picked up the product. Now every month the owed amount ac***ulates and we have to reverse the transaction. Eventually there wont be enough funds in the bank to process the debit order :). We are now considering other legal avenues after many emails and promises (we obviously have all the evidence to support this) as no one at Telkom cares. Their Retention department is simply dysfunctional. They are bullying us and there is simply no way to sort it out via normal channels.