Standard Bank doesn’t care about the little guy

I was ****med out of a lot of money where I sent out an invoice by email and the mail was intercepted. The ****mers sent my client a mail saying that our account had been closed and he was to use our “new” Standard Bank Account for payment. They altered my invoice putting in the Standard Bank details and even sent him a **** proof of bank account whic he duly paid. When we realised that we had been ****med the matter was reported to the SAPS and to Standard Bank. I sent their escalations a mail with a second account number with another invoice that had been altered and another proof of banking sent asking them how this can be allowed to happen. At the end of the day Standard Bank sent our client a letter basically saying they have investigated and money is gone and he will not be reimbursed. How are these bank accounts opened using our company name without the relevant documentation?