On Amazon, always make sure you register your branded products on the Amazon brand registry – this gives you control over the listing and will make it easier for you to get incorrectly listed products removed. On other marketplaces you will need to report an infringement and resolve it with them as two different products shouldn't be using the same GTIN. Marketplaces are cleaning their catalogue of these scenarios as it damages customer trust if the wrong product is received. In any other case, contact us and we can investigate further.