Worn breaks

On Saturday 17 August we bought a car from We buy cars Midstream. While waiting for approval they sold the car without even notifying us. With a big fight and paying the car cash we got the car on Friday 23 August. Yesterday the car starting making a noise, sounding like metal on metal. I took the car to Toyota. All the breaks is worn. I have to pay R3700 to get this fixed. How did the car get a roadworthy certificate and a week later no more breakpads? I did email WE BUY CARS and still waiting for an answer. We didn't even drive 400km with the car yet. This is totally unexeptable!