Hyundai - Original car part exchanged for Hyundai Magna

Hi I have recently faced a problem with power steering of my car and given the car for general servicing and inspection of the power steering by booking through gomechanic app. The service guy from garage said it will cost more than **k for fixing it. To which I instructed to just do the regular servicing and return the car and I can fix it on Hyundai authorize service center at Bangalore. When I took my car to service center upon checking they asked me whether I gave my car to any local vendor recently? I said yes. To which they confirmed that the whote steering wheel base module has been recently changed with a local part and the original Hyundai part fixed is taken away. Now, the original part would cost around **K along with power steering module it would cost me around **K rupees. They have shared some picture of the parts and it clearly shows it is changed very recently and a local brand which is not even functional. When I raised the same complaint with gomechanic service guy and the garage owner they accused me instead and said you might have done that from your end and we didn't do anything. Even they stole some **** rupees of petrol which was in the car while returning. Please take this case seriously as we as a customer blindly believe your service and chose you for service our car.