Scammer!! Be aware!!!

I'm so upset my first posh trading experience turned out to be terrible!!! It made me lost my faith to sell/buy on posh, so I didn't check my account for couple months. This lady made a trade with me for my $400 worth TB bag but she shipped a completely different item to me than we previously agreed. She sounded very willing to correct the error but then turned out to be non-responsive. Please gimme some advices what should I do to get my bag back! Much appreciated!