I want my refund!!!!!!

Mr price is refusing to refund me for the items they didn't deliver. They offered vouchers and I made it clear I don't want vouchers I want my back and I don't understand why they offer customers vouchers when I didn't pay with vouchers. Not only that all along I thought Mr price was refunding undelivered orders like other online stores but to my shock one needs to request if one doesn't nothing gets done basically. This made me look into all my previous orders that they didn't deliver because I thought automatically if an item/s aren't delivered a customer gets their money back but that's not the case with Mr price. I sent them an email with all order numbers for the items I never received but paid for, requesting proof of refund. They basically refused and requested I provide proof of payment yet their system doesn't have an option of receiving orders before paying. How do they explain the other items I received if I didn't pay? They even send confirmation of your order so exactly what are they confirming if I didn't pay? Other online stores provide proof of refund when a customer requests it but Mr price is refusing. I want my money back, holding money that's not yours is not lawful!!!! It's over a month now and I've sent all necessary information but they are ignoring me. This is theft!!!!