2 payments for 1 SINGLE purchase

I bought chicken winglets online and a paid with a Vodacom discount voucher and the balance I paid with my bank card. My order was for a pick up at Nandos Hatfield Pretoria. When I went to pick up my order, to my surprise I was told that I only paid partial of my order with the voucher and that I should pay the balance AGAIN. I went to my banking App to see if the payment did go through and it was showing that it did go through. I should the guy (supervisor or manager ) my transaction on the app and the message that payment was made to Nandos Hatfield but still the guy told me that it was not showing on his side and that I should pay AGAIN since it was not showing (besides the fact that he saw it on my banking app). I paid AGAIN and he didn’t even say leave your name and number in case it shows after you leave so that we can call you to come get a refund. I left and waited patiently until my bank issued a statement. And guess what “THE PAYMENT WENT THROUGH” and I indeed made 2 payments for 1 purchase.

I want my money back. I am pretty sure that the manager saw that there was some extra cash on the statement but he just ignored it. But, I’m not going to “ignore”. I want my money back in full.