Plumbing repair woes

We have recently had work done on one of our properties. This was organised by our property manager. Only one quote was submitted by a plumber and, due to the urgency for the repairs, we accepted the quote. Once the work was complete, our property manager told us he had done a marvellous job. So in good faith we paid without inspecting.

However, a week later we visited the property to do some minor repairs. We discovered the plumbing job was substandard and the repairs were not done properly. Further, our tenants told us the plumber – who turns out to be a friend of our property manager - spent less than half the time he charged us for. He also over charged us for the materials.

We tried mediation through our property manager but they do not support our claims and are covering up for their friend, the plumber. Who do we take the Small Claims Court? The plumber or our property manager? And where can we report our non-professional property manager?