Repair charged without opening a single part on the machine.

After handing in my Chainsaw for a service, I was surprises when I collected it a few days later. First of all I was not called back to collect, I had to inquire myself. I collected the saw and was handed a invoice, stating that the machine has a faulty piston ring And Gasket. The parts have been discontinued. I was charged R350. Upon inspection I noticed that the machine was never opened and inquired why that same saw dust I had on the machine was visibly still there and how the machine was checked without even opening it. The service consultant explained that it was checked through the exhaust. This is a magical company that has x-ray machines that can see inside engines without even opening it. AND THE R350 IS PAYABLE ON THE SPOT BEFORE RECEIVING IT BACK. I am convinced that there was no inspection or any work done on the machine.