Unroadworthy brake pads in 3 months!????????????

Towards the end of March i took my car inn for changing of the brake pads in Hyundai East Rand, the one opposite the East Rand Mall. I was told i cannot change my brake pads only as the discs were also worn out. So i was charged about R8000 to replace both the discs and brake pads. It is now just after 3 months and my car is making this loud brake noise that scares the hell out of me. I never thought i would arrive home safely yesterday as the car was really bad. I am even using taxis to work today since i do not have an alternative transport. So i would like to know if it is normal or even possible that brake pads can wear out in 3 months? I JUST BELIEVE THAT I WAS CHARGED FOR NEW DISCS AND PADS BUT THEY WERE NEVER CHANGED OR THEY SWAPPED THEM WITH USED ONES. That is the only logical explanation i am having. I really am heartbroken as I trusted Hyundai with all my heart but they really have failed me!