Poor unprofessional service

I am disappointed with this dealership. I took a Alfa Romeo in for service and I expected them to do a diagnosis to pick up if there was any other problems with the car because I knew there was but I was not sure what problems they were and they clearly did not do a diagnosis. They just changed the oil and filters and that was it, and this took them 2 days to do so!! The car came back with the same warning light and it smells oil. What is the purpose of diagnosis if they just do a normal service??? Pathetic service indeed!! I also had to keep calling to check if they had the parts available because the service advisor would not call back to update me about the parts I requested to be changed.