Terrible service

Worst ever ! ongoing issue since 15 March with my Renault Duster . Engine warning light came on and took car in. was "fixed" for half hour. Since then car has been in to Renault Fourways 3 times - the light still keeps coming back. Was told that they needed get a part and that i would have to leave my car with them for however long it takes. On Monday I called again and they said i needed to bring it in and that they had a replacement high clearance vehicle for me. I arrived and waiting for 2 1/2 hours and then left with my own car again. Was told they would have a vehicle by Friday (8 Apr). Guess what ? No vehicle yet... Surely there is someone who can sort this issue out ??