Refused Refund

I was refused a refund due to the fact that i had lost a receipt. The item was bought less than 30 days and it was still in the condition i had bought it. I tried to explain that i dont remember where i put the receipt as i was in isolation due to covid, otherwise would have brought this item sooner as i bought the incorrect item. She forced me to take a voucher instead, but i told her that whatever item i wanted isnt in their store and it doesnt make sense that i have to pay another money as if money grows on trees. I asked her to pull a recording of the date i purchased this item as the camera footage will atleast show that i purchased the item there. She refused and told me that their footage was deleted already and it cannot track back to 05/12/2021. She told me about the refund policy and that it was alsoprinted at the back of the receipt, but i asked her how many people does she think go through that refund policy after purchasing an item... I even mentioned the National protection act and that what they are doing is against the law. But she still refund. Please help me get my refund back.