Poor workmanship

I have entrusted this service provider to fix my car. They spent time to fix a number of items on my Audi S3 2002 model. The following is a list of items they worked on:<br> <br> 1. Propshaft - balancing<br> 2. Work around my turbo <br> <br> After they fixed my vehicle, I drove it for a period of 2 weeks, when on a Sunday my coupling (part attached to my propshaft) broke. When investigating the damage by a different service provider, we established that the bolts were not fastened (photos available). To make matters worse, other parts have been damaged as a result of this, leaving me with no vehicle now for 2 weeks. I have had to pay money for a loan car (proof available)<br> <br> To make matters worse, two days after my car broke, my friend's car broke in the same way, yet they have offered to repair his vehicle, and not mine. His car was fitted with a modified same part, whereas mine was fitted with an original OEM part, which should not have failed. I have incurred R25000 losses as a result of this poor workmanship.