Terrible terms and conditions re exchange /returns

Pet plus online has a terrible returns policy.... Bought a jacket for my dog, it was the wrong size, they refused to exchange it for a larger size as I hadn't informed then within 3 days, and they hadn't received the goods within 5 days. Non negotiable. I informed them within a week, but they refused to accept it. In my view a decent company would accept an exchange within 28 days. Beware of this company!