No Feedback on online Purchases

I purchased a tablet online on the 20th of March 2016. I have not yet received my product. Yesterday I had to make calls to the online department who asked me to call the selected dispatch store which was Menlyn branch. Who said they don't have stock and they can offer me another product, which is better, but I have to pay in. Why must I pay in if the product was advertised and purchased this specific product. I had to make numerous calls yesterday and still did not receive any feedback or calls from Incredible. I am seriously not impressed by the service I am receiving. It's 5 days now and no response.