Used iPhones sold as new by iStore Sandton

Istore at 1 Sandton Drive sold me a "new" device , iPhone 13, at a promotional price. On unboxing the device was visibly used, with scratches on the screen but the shop refuses to take responsibility and say i shouldve unboxed it in the shop to prove the condition. this was for a brand new device, and they clearly know it has been swopped for a used one, the promotion is false,