ShopKo online wrong item delivered, no refund for returning it Internet

I ordered a car seat online at shopko that was on sale. But the wrong item was delivered. They sent actually a cheaper product, my credit card was already charged with my original order. Before I sent it back, I called shopko customer service about a refund for returning the package. They granted me a refund! I was happy and sent it back without bothering about the expensive shipping (it was a huge box!). I'm still waiting for my money... for 3 months now and lots of emails back and forth. They don't even reply anymore. I guess they never wanted to give me my money back. At least I got the refund for the car seat, but never for returning the wrong item. I'll never order there again, I don't want to lose more money, time, nerves and patience!