After three visits and four days my bakkie's brakes are worse than ever! ***?!

I took my Corsa Utility to Car Service City in Kyalami for a service. I also asked them to have a look at the brakes because I felt a slight vibration. They reported that the disks seem fine and that there is still 50% pads at the front and 40% shoes at the back, and that maybe it's just brake dust in the rear brake drums.

Upon receiving the vehicle I noticed while driving home that the vibration is still evident when braking. I booked the vehicle in for a complete brake disk replacement and new pads in the front, new shoes and a skimming of the rear brake drums. Upon collection of the vehicle they said that one of the brake shoes was actually broken in two. How they didn't pick that up when I first took the car there I don't know. They told me to drive the car for a few kilometres to 'bed-in' the new brake pads. I did that, but the vibration was still there.

I took the vehicle back a third time, and they had the car for two whole days. Upon collection they assured me that it is perfect. Driving home I noticed that the vibration was even worse. Once I was home I phoned them and told them that it is worse. I said that I will drive to work, just in case it magically improves. On the N1 highway I noticed that when I brake the vibration is worse that even, as if the brakes don't want to release after letting up on the brake pedal. The vibration would continue for a few seconds, and then slowly fade until the next time I brake. I didn't dare going faster than 90km/h because I couldn't trust the brakes.

The only other thing I can do is to replace the drums at the rear, but I'm starting to get annoyed because it's costing me money, it is very unsafe, and despite their guarantees my car is somehow worse now after four days with them than before I took it there at the beginning.