Kia Sonnet Brakes sound

I bought my Kia Sonnet in 2023; The car started making noise every time i reversed. Went to my 15000km service in Kia alberton and made them aware of the sound. I was advised that the brakes are perfect, and they will clean it for the sound to stop. Ever since the sound has not stopped, i mentioned it on my 30000km and the same cleaning they did for my 15k, but sound did not stop. On my 45000km service when I told them the sound is getting worse. I was then advised that I can bring in the car to replace the brake pads. I book an appointment for the replacement and now I'm told I'm out of the warranty plan and they cannot replace it for me without cost. I am being told that the sound is a common complaint for Sonnet cars. I have made the dealership aware of the problem since I got the car, but I was not advised when I stated that I need to replace the pads while I still have the warranty. If this is a common problem, I do not get why should I be the one paying for replacement of the brakes while it's a factory problem.