Vouchers

Hi I bought a pair of tekkies yesterday, woke up today and wanted to exchange them for another pair which is more expensive than the one I bought, I wanted to add and get a different pair, sadly today they are refusing to assist me with making another purchase. I left the tekkies at the store since I wasn't certified with the product and they accepted them. Bare in mind I've never worn them the only thing I didn't have with me was the box, which they remember me leaving at the shop with them yesterday, nobody warned about needing the box for any use and they remember that. They took the tekkies and the slip, wasn't offered to sign anything or giving any explanation if what will happen to those tekkies which were bought by me. ***