Puma Garage Mayville

Stopped at this filling station to fill my diesel vehicle with diesel. While the garage attendant was filling the requested R400 of 50ppm diesel, I was checking the tire pressure of my vehicle. When he was done I swiped for the diesel and left for work. Plus minus 3 hours later when I wanted to drive to go and buy something to eat my car struggled to start. Left for home later, same story. Went to my mechanic straight from work, checked a few things and to my surprise when we pulled the feed pipe coming from my car's diesel tank it smelled like petrol, drained a bit more, still smelling like petrol. Went back to this Puma Filling Station in Paul Kruger Street Mayville Pretoria. Spoke to the manager on duty, showed him the slip of the transaction which stated that 50ppm diesel was filled in my car. He then checked on the system and system also stated that 50ppm was filled into my vehicle. Then the manager requested that a bit of diesel be pumped out of the same nozzel, to our surprise, diesel came out. We then said no this can not be, how did petrol get into my vehicle's diesel tank. We then requested that we take a look at the camera footage of that morning, the manager agreed. Took a look at the footage, realized that the garage attendant pumped plus or minus 12 liters of 93 petrol into my vehicle, when he realized he made a mistake, told the attendant inside the shop to put the transaction through and then only filled my car with the R400 50ppm diesel. So the manager agreed that we should get prices of the parts that is needed. My mechanic put a quote together and sent it to the manager, lots of back and forth, the manager then informed me that only their mechanic should fix my vehicle, if not doing it that way they will not fix my vehicle. Only my mechanic works on my car, been around the block a few time and I know how the people operate, not any mechanic can work on these polos and also dont have the knowledge my mechanic picked up through the years, I only trust my mechanic. This whole incident was not my mistake, the fact that it was handled so dishonestly is also a concern.