Poor Service and charging more than was quoted

I had a break down with my Nissan Navara on the 6th Sept 2017, I had to have my car towed, to the nearest Nissan workshop which happened to be Nissan Milnerton. The pulley on the Alternator was damaged which required a new Alternator. After stripping the Alternator I was informed that I should also replace the serpentine belt and the fan belt, and the serpentine belt tensioner. I asked them how much it would cost and the reply was around R8600.00, I told them they could then go ahead with the job. They then ordered the parts and told me my Vehicle would be ready Friday Afternoon. Friday I received a call confirming that my vehicle would be ready and I could pick it up after 16H30. Around 16H30 I received a call informing me that they had ordered the incorrect Serpentine Belt for my Vehicle. Tuesday I was informed that my vehicle would be ready, only then again to inform me that they had also ordered the incorrect pulley tensioner. It then took them another 5 working days to obtain the correct tensioner, I then receive and invoice of R13908.60. Considerably more than the R8600, that they originally quoted. This without any notification in the change of price.