Frustrated shopper!

I bought a dress on Spree the weekend of the 4-5 August - my dress was delivered that Monday on the 6th of August - turns out the dress was big so I asked for an exchange (return) - item was collected from me on the 7 th of August. On the 17th of August I phoned Spree to find out how far are they with my return and the agent that assisted me told me that the item has passed all the vetting from their side and they will release my dress - nothing! I phoned on Friday the 25th of August in the morning and was promised my item would be delivered later that day and still nothing - its the 27th of August and I still don't have my item - which I paid for long ago! This is ridiculous to have to wait for so long for an item!