Spree exchange

I bought pants and received it on 23 August 2018 from Spree which I needed to exchange. After several phonecalls and emails and no collection I eventually couriered the pants back myself. They waited for the return parcel to being back with no success again. Another week went by before the new parcel arrived only to discover they did not exchange my parcel they just resent it back exactly the same way we send it. They've put it in a new bigger bag with the old parcel inside. Email and call them. With no help whatsoever. Only receive rating service emails. It is now a month since I've bought it and tried to exchange.