Dissatisfied due to items purchased not being taken back

Dissatisfied due to purchase made in Centurion

Approximately a month ago, I made 2purchases in 1 day of about R7k and still returned 2days later for a further purchase. I’m at a point whereby I realise that I bought some unnecessary stuff this would like to exchange them for things I need, the problem is that I’ve misplaced the invoice concerned but price tags are still in tact and since I used a bank card to do my purchase, I can bring it back as supporting evidence.

Having called the store, spoke to Bongani too who identified himself as the store manager assistant, they mentioned that the store policy requires that the proof of purchase, in a form of an invoice must be brought along. No alternative exist. How can that be the case? I’ve delayed my next purchase as I would like to get credited for items I’ve got to return prior to topping up on my purchase.

Please advise urgently