Faulty tablet delivered

Elite mobile phoned me with specials and offers from Vodacom. I wasn't interested in any of the products but in the end I decided on a Samsung Galaxy Tab E 9.6. They offered me a very good deal. I received the tablet within 3 days on Monday the 12th of February. They said it will take about 48 hours to activated the service. On Wednesday the 14th I realised that the sim card does not read/register on the tablet. I phoned Elite mobile immediately and the lady suggested that maybe I'm not putting it in correctly and I must take it to a Vodacom shop. I stay quite far out from town and only manage to get to a store on the Friday the 16th. They said that it seems to be the wrong size sim and it does not read on the tablet. Friday afternoon I phone Elite mobile and after a bit of a struggle to get them to understand the problem they agreed to come and collect the tablet but it will take up to 14 days to collect it. They were very quick to sell this product to me and delivered it but when I have a problem it takes 14 days to collect it. In the mean time I'm paying for something that I can't use and I don't even know if they will replace it. WHAT DO I NEED TO DO to sort this out immediately. This is my second bad experience with Elite Mobile.