No delivery and no response!

After having been contacted by the MTN upgrade centre, and having agreed to a new phone, nothing has been received. There was a call from them saying that the particular phone was out of stock but that a slightly lesser one was available, I agreed to this. Despite me having written on numerous occasions over the months, and despite insulting them, still no response. They are quite happily taking my money!! Their advertising is ********** and their practice is that of a *****!!