Customer service inefficiencies left me stranded!!

From the time I purchased my vehicle from the Edenvale GM on 21/07/2014 up until now, I have received the worst customer service from all these dealers. GM staff have an attitude of 'its not my problem'. They act as though they are doing you a favor yet it their function to provide good sales & after sales service. They are quick to pass the buck for efficiencies in their processes. Today was just one of those days. My car broke down & I was told (@CrestaGM) that the cambelt needed replacing - I questioned how same was not diagnosed at my car service on the 23/09/2015 (