Slazenger Deducting Cost of Gift After Receiving Defective Item

Slazenger sent me a pair of shoes that were not in good condition. They admitted their error and took back the shoes. However, when they refunded me, they subtracted the cost of the socks they had given me as a gift. Basically, what they're saying is, "We're giving you a present, but later on we'll ask you to pay for it, even though it was our mistake." To be honest, I've never seen a business approach like this before. It's really confusing and annoying that they would give a gift and then take it back, especially when they were the ones who messed up in the beginning. This whole thing has made me wonder if Slazenger is really doing business in an honest way.