Wish I could give less stars

I bought 3 pairs of socks at H&M Somerset mall, and when I got home one pair was a larger size than the others. I took it back to exchange and was told they can't exchange it because I had removed the little plastic piece tying the socks together, thus "removing it from its original packaging". They refused to exchange it because "its policy". Regardless of the socks not having been worn (other than trying them on to realize they're not the right size) very disappointing service