Wonderboom Mercedes Benz bad service

Buoght GLa in 2017, they assured me that is with run on flat tyres, only to find that they were not, i complained the changed them, still with wrong tyres, even if they rold me that they were run on flat. The tyre service provider called me for after service and he revealed that those tyres were not run on flat. They eventually changed them with the correct tyres after a long run around. When i bought my car, they didn't give me a spare key, however they added key guard insurance which will not work if i didn't have spare key. The told me to bring Natis documents which i ordered and were delivered, but still they couldn't give me a spare key. I have been up and down with them, the just told me that they lost my documents. When the key guard insurance expired, i couldn't renew it bcoz i didn't have spare key. I have been taking my car to them for service, all the time i reported the engine light reflecting, they always promised to fix it, but they couldn't, recently, when i reported the ight again, i was told to pay for diagnostic again so that they check the problem. This branch' s service is extremely bad that my latest service, i had to go to another branch, but then, they couldn't work on the engine light bcoz it was a recurring problem otherwise i must pay them for checking it. This has affected my car performance badly, it looses power. I complained many time after every service. To date, my car's engine light is still on and i still don't have a spare key. Kindly intervene.