Pathetic disaster

Took my car for 90 000 km service, two days later I heard some noise in the car. Took the car back to them and they said brake pads have won out. What have they been doing in that service if they did not check braking system. Now both front and rare brake pads have been replaced. Wonder if there was any problem with them as the car is still having the same problematic sound. I even feel they don't know what they are doing, just the trial and error