Phones and other electronics have to come back unopened, with the seal intact and in the original packaging. Once a product has been opened, had its seal removed or been used, no refund is given unless a manufacturing defect is found. If it is, send back the box, manuals and every accessory, and Carrefour chooses whether to repair, replace or refund it.
Large appliances, including washing machines, fridges and TVs, can be fully refunded if returned no later than 7 days after delivery with the seal unbroken. Faults that show up later fall under the manufacturer’s warranty.
Source: Carrefour help center: Electronics returns