More than 4 months later I'm still waiting

I took my 2015 Duster to Renault Centurion for a faulty Medianav to be fixed in September 2015, if not earlier. Etienne informed me that they could not fix it, but since it was still under warranty they will order a new one to replace and I should expect their call within 14 working days. In November 2015 I still had not heard from them, when I called he gave me another 14 days to wait and said it was still on its way. Well, it's 20/01/2015 now and I'm still waiting. Just called them and guess what, the guy has resigned and they still want to check if my car is under warranty. So the process begins from scratch. Another four, five or ten months of waiting? Poorest of services I've ever received. By the way, the Medianav contributed to my decision to buy the Duster instead or other offerings out there and that's the one thing I'm forced to live without. I should have known better.