bad Service

I bot a 2016 Toyota Corolla Quest on the 25 Nov 2017 with 31000 KM at this branch. I only drived 3ooo KM and I had to change the back brike pads by 24 Dec 2017. While the dealer told me that 30000 Km service was done on this car and brikes were checked during the 30000 KM service.