Poor mechanical work

Poor mechanical work

Took in my car for service on the 21 August On the 1st September my car battery had a leak . Due to corrosion from battery acid, I have to replace the negative control unit. This is not Bosch fault. But how do you service a car , which includes changing air filters and miss that . I don't understand how a mechanic can miss that and the negative impact it can have on a vehicle..

This Very poor service, because I would trust that necessary things were checked even the visible ones to the naked eye