Short version - I wanted to replace a shoe due to a defect (never used, bought them the night before) and they asked me to pay extra because the price has changed! Furthermore when I said that I wont pay extra, they refused to give me the shoe with the defect as well so I went home without the shoes (they refunded the initial amount). On their website it is clearly written that you can request exchange of a defective product. I wrote to Decathlon Bulgaria, then I called them (as I thought it is just a misunderstanding) - the answer was that this is out of their scope and that I have to talk with a manager in the store, without pointing any name or contact information of him.
************** that's the number of the query that I've raised to Decathlon Bulgaria)