Sold 2 Right Feet ?

I bought a pair of sneakers from your Mall of Africa branch and arrived home to find that I had been sold 2 right shoes. I understand that mistakes happen, especially during a time as busy as the festive season, but I can't help but feel quite irritated by this. It's a costly inconvenience for me as I live quite s distance away from the Mall and will now have to spend more money than I spent on the sneakers just to go swop them out. I need to know how I can best accomplish this at the least amount of cost and inconvenience to me please.