The distance selling rules give you the right to return (for no reason) within 14 days, under the The Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013.
It may be different in Belgium, but getting shouty when you're wrong isn't a good look.
Right to cancel
29.—(1) The consumer may cancel a distance or off-premises contract at any time in the cancellation period without giving any reason, and without incurring any liability except under these provisions—
(a)regulation 34(3) (where enhanced delivery chosen by consumer);
(b)regulation 34(9) (where value of goods diminished by consumer handling);
(c)regulation 35(5) (where goods returned by consumer);
(d)regulation 36(4) (where consumer requests early supply of service).
(2) The cancellation period begins when the contract is entered into and ends in accordance with regulation 30 or 31.
(3) Paragraph (1) does not affect the consumer's right to withdraw an offer made by the consumer to enter into a distance or off-premises contract, at any time before the contract is entered into, without giving any reason and without incurring any liability.
Normal cancellation period
30.—(1) The cancellation period ends as follows, unless regulation 31 applies.
(2) If the contract is—
(a)a service contract, or
(b)a contract for the supply of digital content which is not supplied on a tangible medium,
the cancellation period ends at the end of 14 days after the day on which the contract is entered into.
(3) If the contract is a sales contract and none of paragraphs (4) to (6) applies, the cancellation period ends at the end of 14 days after the day on which the goods come into the physical possession of—
(a)the consumer, or
(b)a person, other than the carrier, identified by the consumer to take possession of them.
(4) If the contract is a sales contract under which multiple goods are ordered by the consumer in one order but some are delivered on different days, the cancellation period ends at the end of 14 days after the day on which the last of the goods come into the physical possession of—
(a)the consumer, or
(b)a person, other than the carrier, identified by the consumer to take possession of them.
(5) If the contract is a sales contract under which goods consisting of multiple lots or pieces of something are delivered on different days, the cancellation period ends at the end of 14 days after the day on which the last of the lots or pieces come into the physical possession of—
(a)the consumer, or
(b)a person, other than the carrier, identified by the consumer to take possession of them.
(6) If the contract is a sales contract for regular delivery of goods during a defined period of more than one day, the cancellation period ends at the end of 14 days after the day on which the first of the goods come into the physical possession of—
(a)the consumer, or
(b)a person, other than the carrier, identified by the consumer to take possession of them.
Cancellation period extended for breach of information requirement
31.—(1) This regulation applies if the trader does not provide the consumer with the information on the right to cancel required by paragraph (l) of Schedule 2, in accordance with Part 2.
(2) If the trader provides the consumer with that information in the period of 12 months beginning with the first day of the 14 days mentioned in regulation 30(2) to (6), but otherwise in accordance with Part 2, the cancellation period ends at the end of 14 days after the consumer receives the information.
(3) Otherwise the cancellation period ends at the end of 12 months after the day on which it would have ended under regulation 30.
Exercise of