Based on the European Union regulation of 15th February 2016 disputes related to purchases online across the EU will be possible to resolve through the ODR platform, which you can access here.
If you encounter a problem during an online purchase within the EU (i.e. defective product, inability to replace the product, etc.) you can submit your complaint immediately using the link above.
The platform can be used by both customers and traders, and complaints can be lodged in any of the 23 official EU languages.