Air carrier Captain reported the ground crew left the aircraft without giving instruction to set brakes or clearance to start engines during the push back from gate.

Narrative

B767-400 pushback from gate. Initial contact from pushcrew was not SOP. After I received push clearance; I said 'cleared to push; east taxi'. The ground response was cleared to push. After initial push; Ramp instructed us to 'push deep abeam Taxiway XX'. I vocalized exactly those instructions and my ground crew response was; 'yes'. I repeated the instructions and received no reply. We suspected the push crew was new and training; as well as the Marshaller. We pushed abeam Taxiway XX and the ground crew never vocalized a response. Our ground crew disconnected the aircraft and left without any required commands such as 'set brakes; cleared to start engines; or disconnecting headset'. I held the brakes and the aircraft did not roll forward. I flashed my taxi light twice and received no reaction from ground crew or Marshaller. I tried again and used the ground call horn twice. No result. We tried to use hand signals to other marshallers to signal we couldn't hear; they waved and turned around. At this time I set the parking brake. I asked the First Officer to contact ZZZ Ramp to clear our aircraft for engine start. I asked the Relief Pilot to call ZZZ Operations and relay information to our ground crew about the noncompliance. Operations reported they were unable to reach them; but would forward the information.