Online Purchase

I ordered a 2 coffee percolators online. When it was delivered it was not the correct product. Phoned customer service and they said it was a technical glitch on their system and the wrong product was advertised and they will refund me. Told me to return the product to the nearest store and they will refund me. I returned the product just to be told that they will submit a refund on my behalf which will take 7 - 14 working days. Its been 3 weeks since I returned it and more than a month since I made the purchase. Every time I follow up on my refund it still has not been processed. I've also sent my details to them to no avail. I'm now fed up!!