Bosch fail to call for authorisation before service

I took my car to service on the 28 Jan, they service my car without looking for authorisation. The call me after they complete with service telling me that I be have to pay 3000 . They didn't sent me quotation. I told them before I leave they must call my insurance for authorisation but they fail to do so. And they replace plugs without notifying me. I have forced to pay for plugs replacement or else they don't give me my car. that was poor customer service From Bosch service VB Moreleta park Pretoria