Through the discussion message chat window, discuss the products with the seller and ask to replace the items. If the seller doesn't agree then the buyer will have to click the "Open a Dispute" button on the transaction screen during the Inspection Period. 

Doing this Bitxoe administrator will get notified about the disagreement and review the transaction details through special access to the transaction page. Bitxoe.com will then send amendment emails to both parties and ask both to make the adjustments and give instructions after the Buyer and Seller have replied to the amendment email.