Got ripped off from the MP

I recently bought a DRD build from the MP and when I unboxed it, it had another box and inside that another box which was empty except for a note to go to DRD to exchange it at their gacha station. But not to open the box the note was in. No indication on the ad. No response back from the seller. Since I already unboxed it I can’t exchange it. I don’t even know if DRD still has their gacha exchange anymore not that it matters now.

What can I do?