There are two dummy pins for the non-used phases in the car's charge port socket. Only one phase has an actual conductor which supplies the on-board single phase charger. They use the same socket design for single and 3-phase, just change the number of active pins in use.
You have unfortunately been sold the wrong charge station for your vehicle, and given it's an MG branded one that's possibly a dealer error which they really should come to the party to help correct. Unless you insisted you knew better by ordering the 11 kW 3-phase charger.
To charge at your car's full rated AC power capacity you either need a 22 kW 3-phase charger (which is overkill for this car but you may have other vehicles which can take advantage) or a single phase charger capable of delivering 7 kW. Either will require wiring and breakers etc suitable to carry the higher currents.
Your current charge station will still work but your charging will always be limited to 3.x kW. For many people that's going to be adequate most of the time but if you want/need to charge at the car's full rate then you'll need a different charge station.
The only MG 4 with 3 phase charging capability is the Essence 77 Long range.
Yep, that correct for Australian models.
OP quoted an Australian model name and their profile shows they are located in Perth, Western Australia.
Some of the equivalent 64 kWh models in Europe do have 11 kW 3-phase chargers.
Separate comment:
I'm not sure about WA, but there are some restrictions on installing EV charge stations in QLD (which many ignore) - any single phase charge station above 20 A is supposed to be on a separately metered controlled load circuit only. It's dumb in many ways, but mainly because that immediately prevents consuming your own solar PV.
What is confusing me is why he's only getting 3 Kw though.
The car may be using some of the available power for other things, like charging the 12 V battery.
