I bought a product they sent a wrong colored item

I bought a product they sent a wrong colored item. I asked them to exchange the product that I have ordered or blue colored item. They did not do what I have asked, the lady who cam to collect left while I was on a call with the lady from the westrand hub, she hang up and left me with no clear indication of what I must do with the product. I am clueless what is the next step, how will this get resolved and their cape Town head office they pick up say nothing and hang up. This was the worst experience ever.