Toyota Yaris Squeaking Brakes

I’m new here and I hope someone from you can help me. And although I bought a Toyota Yaris II SOL 1.0 with (disk brakes at the rear) that I bought last year in Septmeber. He has now about 20,000 km on it. I noticed now that the brakes squeak and since I was anyway at the tyre change I asked Toyota if this is normal, customer service consultant said no, they look at it, they have then gemint they slid off the brake pads. Only now d As squeaking up much more often and has also become much louder so it is now worse than before. Before it was rather rare, it happens when I let it roll out at the traffic light and then gentle brake. I only called and they meant they can look at this but can not say if this still goes on guarantee, because maybe they have to change the brake covers you are a wearer, would that then be normal that you change the brake receipt after 20,000 km ? I h abe ehrlcih said no idea, because it is my first own car I have been out for many years without it. I didn’t really want to let it happen if they want to change and I have to pay for it, because actually the squeaking before was not so bad and after the surgery of which it has become significantly worse. How do you see that ?