Endangering peoples lives

My fiance and I went and rented a car from Budget car rentals at OR Tambo a few days back. When i picked up the rental it had a warning light for tyre pressure. When i went to ask about this issue at the desk i was told it was normal with their ford cars that this light came on. I thereafter proceeded to the nearest garage where i got the tyres checked. Following morning i woke up to find my tyre was half flat and when i took a closer look both front tires on this vehicle were finished and were showing signs of tears in them. This is a vehicle i had planned to use for the next seven days to travel long distance around South Africa with my fiance and some friends. I then had to take back the car to the airport where I was told i would still be charged for petrol i used to bring the car back even though it was their fault i had to travel the distance back again. My biggest concern is not the petrol i used to return the car, my biggest issue is the attitude shown towards this matter. I have written a mail to all management however nothing was ever done. I find this unacceptable from a rental company. Those tyres could have popped at any moment and lives could have been lost. I am very disappointed to say the least!