Not fixing Isuzu bakkie oil leak

I bought a 2008 Isuzu double cab from them in May 2015. Today is 17 March 2016. Firstly they advertised that the bakkie had a full service history which it did not. Soon after I bought it I realized that it had an oil leak. After meeting with the owner Andre, he promised to fix the problem. Since then the bakkie has been back with them at least 4 to 5 times and still the oil leak has not been resolved. Now when I ask about it and message Andre, he doesn't respond. He did at one stage suggest that I buy another vehicle from them, which I was willing to do, but it has been 2 weeks after I have showed interest in a vehicle and once again Andre has gone quite. Also I traded in another car for the Isuzu only to find that I had to chase them down to settle the car, apparently they forgot / slipped through. I have a backup of emails and WhatsApp communications as evidence which will gladly be made available to anyone who doubts that this is an honest review. Their communication in all formats are shocking, from the first day I've started communicated with them.