GM does not take responsibility for defects on new vehicles

I have a chev utility which is 2 years old still under the 5 Year warrenty plan. I've had endless problem with the vehical from the gear box to head light defects. But never the less I gave them the opportunity to repair the defects. Recently when taken in for a yearly service I noticed that 1 tail like bubbling so I brought this to there attention. When fetching the vehical the agent says that he Manager took the decision not to put in a warrenty claim due to the light being damage was the car shampoo that was used to I found this strange that since only 1 tail light got damaged by this shampoo. The same day I contacted gm south Africa and they where just as unhelpful as the manager. They send me to panel shops to get opinions. Then to the dealership more that 4 times to get different people from there grop to give options. This was a waste of my time and worse hours lost. It's 3 months later and I'm still waiting for feed back. They never call to follow up I had to keep on there case to order to get help. My advice never buy a GM vehical they don't never honor the warrenty.