Strange grinding noise in 2015 Kia Rio

There is a grinding noise in my 2015 Kia Rio 5-door hatch. I have had the car checked by Kia's mechanics five times and they can't fix the problem. They told me that the handbrake was too tight and that the handbrake was engaged all the time, even when it was off. It was like this from day one. I have done 20,000 km in the car. They should have found it in the pre-delivery, if they did it. I can't get any satisfaction. Where do I go, what do I do?