Parcelforce

Wrong item with the right tracking number?

Parcelforce have delivered the wrong item and won't accept responsibility for it because I signed for the item? The error lies in the fact that they covered someone else's name, address and tracking number on a random box with all my details meaning I got their item. Who knows where mine is. But because I didn't open the box on my doorstep I'm £160 out of pocket? Not good enough.