Unexpected Poor Service

My car’s brake pads and discs were worn out. I instructed Renault Centurion to replace them. Even before this my ABS light and what I think is the traction light was not on. After they replaced the discs and pads I saw the lights coming on. I could not take the car back to them as I collected it on Saturday. I took it back to them this morning first thing and the technician drove around with the car for a bit and then came back to tell me that it is the drive shaft that is the issue. This is very surprising as this would have been something that they should have seen from the beginning. I explained to him that when I brake the brakes intermittently lose grip meaning they miss and make a funny clucking sound. He again went to the drive shaft excuse. I told him why then weren’t the lights on before I brought the car in even with my discs and pads worn out? He again told me it was the drive shaft. They did not even bother to have a look at what they might have done wrong and just wanted to get rid of me. The service and technical expertise and Renault Centurion is dwindling and I bet I am not the only customer complaining about such incidents.