Terrible service!

I was involved in a car accident and took my car for repairs at Precision&Son in Pretoria on 22 February 2016.Mercedes keeps supplying the incorrect part therefore the panel beater is unable to fix the car up until now.Mercedes is in the process of sourcing the part from Germany and cannot provide with time lines of when the part will be delivered. My courtesy car from the insurance has lapsed and I have tried numerous times to request a courtesy car from Mercedes since the delay in repairs is due to them outsourcing the incorrect part. I have been sent from pillar to post by the various department of Mercedes and none of them could assist .I finally called the customer care line with my request with no success. The call centre agent promised to call me back on Friday 08 April but nothing . What's annoying is that I must be the one following up on them.The last customer care agent told me they don't do that but he will call me back but he never did! It cannot take 2 months to fix a car!Buying a Merc was a worst decision ever! There is a serious lack of customer care. I am unable to get around without a car and I don't know when I will get the car back.Totally unacceptable!!