Nedbank authenticated an EFT incorrectly!

Hi All, it is a sad day for me. I have a new small Biltong shop, in Western Cape (2weeks old), I received a huge order from a Private person from Johannesburg, did an EFT, from Nedbank. I called Nedbank and was assisted immediately, the Agent and Teamleader looked at the Proof of Payment and declared it as authentic, BY EMAIL, ONLY then did i release the stock. And that same day the same client requested a second consignment. AGAIN I .went through the same procedure by calling Nedbank, and the lady again assured me the POP is legit . To my sad realization...NO monies in the account 3 days later, the client is not answering his phone, I went in to the Branch closest to me, again the lady at the counter said it is legit, and that I have to go to my bank Capitec... Got to Capitec, they say no you should go to Nedbank, there is no monies in any accounts of mine, or even in a waiting period. I would never ever had my stock couriered to this person, if I did not have the ok from a well known bank like NEDBANK, Please advise what I can do to resolve this, it is a loss of over R20k. Please someone can you assist?????