Appalling customer service

I requested a return of an electrical item purchased online at Makro on March 1, it was subsequently collected and returned to the Marketplace supplier. I was informed that it was to be replaced but to date I have not received the item nor a refund. The call centre are hopeless. I was called on March 27th by a representative of Makro promising feedback but have heard nothing since then and his phone just rings. I simply don't know what to do next.