If you have a problem with a company established outside Europe, it is more difficult to find a solution, particularly due to differences in language and legislation, as well as distance.
First contact the seller in writing, preferably by email. Gather all documents related to your purchase, explain the problem and ask for a solution.
If unsuccessful: your credit card issuer protects you via a chargeback (dispute form within 3 months of the transaction). You can also report to the FPS Economy and consult ECC Belgium's advice.
Dispute a purchase: mijnkaart.be — for Visa/Mastercard, PayPal and Klarna.