Where are the Tax Invoices???????

No-one at DHL can answer me as to WHY Tax Invoices are not at the very least included with the shipment on arrival?? They send out Proforma's for upfront customs and duty payments etc, but NEVER send the Tax Invoice! Why??? I spend more time trying to get the Tax Invoices from them than any other logistics company. We tried to open an account so I could download the Invoices, but as our supplier sends on their account it did not work. Why is it such a run around? SARS do NOT accept any proformas - so why use them?? Obv I am going to make payment - otherwise no delivery - so send me a Tax Invocie. Their emails just bounce back and the customer care department just ignore requests/ No point emailing the "management" as that is a generic email and I doubt anyone reads it as I have yet to receive a response. Absolute nightmare.