CASTELO refusing to REFUND SHOE FALSELY ADVERTISED

I bought a lovely shoe (online) on sale which was my size. It is a patent strappy high heel sandal with ankle and toe straps only. The store is in JHB and I am in CPT. Upon receiving the order, I find that the straps of the shoe are so small (patent straps don't stretch and its like plastic) my toes could hardly go through the straps at the toe. Naturally I want to return the shoe because this (sizing of the toe strap) was not mentioned on the site when purchasing the shoe. I dont care about there no cash refund because they failed to mention the fact that the shoe patent strap shoe would be small at the toes! If I place my foot on the strappy shoe IT FIT, it just cant go through the toes. The issue management has is that I received the shoe and "I should have bought the correct size" WHICH I HAD. A size 4 would have been too small and a size 6 would have gone through possibly but been too big as the toes part of the shoe would be too long and cause my foot to slide forward!!!!! Make it make sense ??? THIS IS NOT MY FAULT! I want my money back! And I DONT want a voucher to buy something else, I want NOTHING to do with this store EVER AGAIN!