Disappointed client

I am highly disappointed on how they treat their customers,I bought stuff from their App and only to realize that I made a mistake on the order that I've purchased,then I went through their exchange policy and it stated very well that as long as the items are still in the same condition from the seller we are allowed to exchange or return for refund but after asking for exchange nothing was done,I ended up selling the stuff to someone else to cover the costs. I bought the right items now and they delivered even though it took a bit longer but I eventually got my stuff.