Shocking service from Tata/KIA dealership

We bought a Tata Super Ace in 2013 from KIA Edenvale, which we use to deliver certain stock items to our stores. We have been unable to use it since the 6th of June 2015 due to the Dealership's inability to successfully repair this vehicle. The problem started in March 2015 where the starter motor was no longer operational and we were told that there was no stock available to repair our vehicle so we would have to push start our vehicle. Eventually after complaining via various emails and phone calls to Grant and Christelle (Tata customer care), the starter motor was then sorted out and we could pick up the vehicle on the 24th of June 2015. The vehicle would not start. Then the cambelt had to be checked and then we were advised that the exhaust manifold gaskets was the problem. This morning Christelle informed us that they are waiting for the exhaust flexi pipe on back order from India. Without this vehicle we find ourselves in a position where we are actually losing money as well as our time. We find this situation totally impossible and demand that this be sorted out immediately! This is not an unreasonable request.